PS. In case anyone is interested, here are the error reports from my 
last two problems:

-------------------------------------------------------------------

10 April 2007 11:50:22 pm

VM: Win32 - a SmalltalkImage
Image: Squeak3.10alpha [latest update: #7083]

SecurityManager state:
Restricted: false
FileAccess: true
SocketAccess: true
Working Dir C:\Squeak\squeak-dev
Trusted Dir C:\Squeak\squeak-dev\andreas
Untrusted Dir C:\My Squeak\andreas

UndefinedObject(Object)>>doesNotUnderstand: #pathJoin:
	Receiver: nil
	Arguments and temporary variables:
		aMessage: 	pathJoin: 'C:/Squeak/squeak-dev/squeak-dev-beta-107.image'
	Receiver's instance variables:
nil

RioKernel>>full
	Receiver: (RioKernel new: 'C:/Squeak/squeak-dev/squeak-dev-beta-107.image')
	Arguments and temporary variables:

	Receiver's instance variables:
		value: 	'C:/Squeak/squeak-dev/squeak-dev-beta-107.image'

RioKernel>>parent
	Receiver: (RioKernel new: 'C:/Squeak/squeak-dev/squeak-dev-beta-107.image')
	Arguments and temporary variables:

	Receiver's instance variables:
		value: 	'C:/Squeak/squeak-dev/squeak-dev-beta-107.image'

RioKernel class>>getDefault
	Receiver: RioKernel
	Arguments and temporary variables:

	Receiver's instance variables:
		superclass: 	RioWin32
		methodDict: 	a MethodDictionary(#/->a CompiledMethod (502) #asRio->a 
CompiledMet...etc...
		format: 	132
		instanceVariables: 	#('value')
		organization: 	('as yet unclassified' / printOn: setPath: 
splitToPathAndName:)
(...etc...
		subclasses: 	nil
		name: 	#RioKernel
		classPool: 	a Dictionary(#Default->nil )
		sharedPools: 	nil
		environment: 	a SystemDictionary(lots of globals)
		category: 	#'Rio-Kernel'
		traitComposition: 	nil
		localSelectors: 	nil


--- The full stack ---
UndefinedObject(Object)>>doesNotUnderstand: #pathJoin:
RioKernel>>full
RioKernel>>parent
RioKernel class>>getDefault
  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
RioKernel class>>startUp
RioKernel class>>initialize
MCMethodDefinition>>postload
MCMethodDefinition(MCDefinition)>>postloadOver:
[] in MCPackageLoader>>basicLoad {[:ea | ea   postloadOver: (self 
obsoletionFor: ea)]}
[] in OrderedCollection(SequenceableCollection)>>do:displayingProgress: 
{[:each :i |  bar value: i.  aBlock value: each]}
OrderedCollection(SequenceableCollection)>>withIndexDo:
[] in OrderedCollection(SequenceableCollection)>>do:displayingProgress: 
{[:bar | self   withIndexDo: [:each :i |     bar value: i.    aBlock 
value: e...]}
[] in ProgressInitiationException>>defaultMorphicAction {[result := 
workBlock value: progress]}
BlockContext>>ensure:
ProgressInitiationException>>defaultMorphicAction
ProgressInitiationException>>defaultAction
UndefinedObject>>handleSignal:
MethodContext(ContextPart)>>handleSignal:
MethodContext(ContextPart)>>handleSignal:
ProgressInitiationException(Exception)>>signal
ProgressInitiationException>>display:at:from:to:during:
ProgressInitiationException class>>display:at:from:to:during:
ByteString(String)>>displayProgressAt:from:to:during:
OrderedCollection(SequenceableCollection)>>do:displayingProgress:
[] in MCPackageLoader>>basicLoad {[additions   do: [:ea | self 
tryToLoad: ea]   displayingProgress: 'Loading.....]}
BlockContext>>on:do:
[] in MCPackageLoader>>basicLoad {[[additions   do: [:ea | self 
tryToLoad: ea]   displayingProgress: 'Loading....]}
BlockContext>>ensure:
MCPackageLoader>>basicLoad
[] in MCPackageLoader>>loadWithNameLike: {[self basicLoad]}
[] in MCPackageLoader>>useChangeSetNamed:during: {[aBlock value]}
BlockContext>>ensure:
MCPackageLoader>>useChangeSetNamed:during:
MCPackageLoader>>useNewChangeSetNamedLike:during:
MCPackageLoader>>loadWithNameLike:
MCVersionLoader>>load
MCVersionLoader class>>loadVersion:
MCVersion>>load
MCMczReader class(MCVersionReader class)>>loadVersionFile:
[] in UIMonticello>>installFileNamed: {[:reader | ^ reader 
loadVersionFile: filename]}
SystemDictionary(Dictionary)>>at:ifPresent:
UIMonticello>>installFileNamed:
UInstaller class>>installFileNamed:
UPackage>>install
UConfiguration>>installPackage:
[] in UUniverseBrowser>>doInstall {[configuration installPackage: p]}
[] in Utilities class>>informUser:during: {[aBlock value]}
MVCMenuMorph>>displayAt:during:
Utilities class>>informUser:during:
[] in UUniverseBrowser>>doInstall {[:p | Utilities   informUser: 
'installing ' , p printString   during: [confi...]}
OrderedCollection>>do:
UUniverseBrowser>>doInstall
PluggableButtonMorph>>performAction
...etc...

-------------------------------------------------------------------


10 April 2007 11:49:55 pm

VM: Win32 - a SmalltalkImage
Image: Squeak3.10alpha [latest update: #7083]

SecurityManager state:
Restricted: false
FileAccess: true
SocketAccess: true
Working Dir C:\Squeak\squeak-dev
Trusted Dir C:\Squeak\squeak-dev\andreas
Untrusted Dir C:\My Squeak\andreas

OrderedCollection(Object)>>error:
	Receiver: an OrderedCollection()
	Arguments and temporary variables:
		aString: 	'Object is not in the collection.'
	Receiver's instance variables:
		array: 	#(nil nil nil nil nil nil nil nil nil nil)
		firstIndex: 	3
		lastIndex: 	2

OrderedCollection(Collection)>>errorNotFound:
	Receiver: an OrderedCollection()
	Arguments and temporary variables:
		anObject: 	[] in 
MultiSelectHierarchicalListMorph>>selectByExpandingThroughColle...etc...
	Receiver's instance variables:
		array: 	#(nil nil nil nil nil nil nil nil nil nil)
		firstIndex: 	3
		lastIndex: 	2

[] in OrderedCollection(Collection)>>detect: {[self errorNotFound: aBlock]}
	Arguments and temporary variables:
		aBlock: 	[] in 
MultiSelectHierarchicalListMorph>>selectByExpandingThroughCollect...etc...

OrderedCollection(Collection)>>detect:ifNone:
	Receiver: an OrderedCollection()
	Arguments and temporary variables:
		aBlock: 	[] in 
MultiSelectHierarchicalListMorph>>selectByExpandingThroughCollect...etc...
		exceptionBlock: 	[] in OrderedCollection(Collection)>>detect: {[self 
errorNotFou...etc...
		each: 	nil
	Receiver's instance variables:
		array: 	#(nil nil nil nil nil nil nil nil nil nil)
		firstIndex: 	3
		lastIndex: 	2


--- The full stack ---
OrderedCollection(Object)>>error:
OrderedCollection(Collection)>>errorNotFound:
[] in OrderedCollection(Collection)>>detect: {[self errorNotFound: aBlock]}
OrderedCollection(Collection)>>detect:ifNone:
  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
OrderedCollection(Collection)>>detect:
[] in 
MultiSelectHierarchicalListMorph>>selectByExpandingThroughCollection: 
{[:eachItem |  morph := siblings     detect: [:itemMorph | itemMorph 
complexC...]}
OrderedCollection>>do:
MultiSelectHierarchicalListMorph>>selectByExpandingThroughCollection:
WhiskerWindow>>selectClass:
WhiskerBrowser class>>openExistingBrowserOnClass:selector:
WhiskerBrowser class>>openExistingBrowserOnClass:selector:
WhiskerBrowser class>>openExistingBrowserOnClass:
[] in TextMorphForShoutEditor(ParagraphEditor)>>browseIt {[aSymbol first 
isUppercase   ifTrue: [anEntry := Smalltalk       at: aSymbol...]}
TextMorphForShoutEditor(Controller)>>terminateAndInitializeAround:
TextMorphForShoutEditor(ParagraphEditor)>>browseIt
TextMorphForShoutEditor(ParagraphEditor)>>browseIt:
TextMorphForShoutEditor(ParagraphEditor)>>dispatchOnCharacter:with:
TextMorphForShoutEditor(TextMorphEditor)>>dispatchOnCharacter:with:
TextMorphForShoutEditor(ParagraphEditor)>>readKeyboard
TextMorphForShoutEditor(TextMorphEditor)>>readKeyboard
[] in TextMorphForShout(TextMorph)>>keyStroke: {[editor readKeyboard]}
TextMorphForShout(TextMorph)>>handleInteraction:fromEvent:
TextMorphForShout(TextMorphForEditView)>>handleInteraction:fromEvent:
TextMorphForShout(TextMorph)>>keyStroke:
TextMorphForShout(TextMorphForEditView)>>keyStroke:
TextMorphForShout(TextMorph)>>handleKeystroke:
KeyboardEvent>>sentTo:
TextMorphForShout(Morph)>>handleEvent:
TextMorphForShout(Morph)>>handleFocusEvent:
[] in HandMorph>>sendFocusEvent:to:clear: {[ActiveHand := self. 
ActiveEvent := anEvent.  result := focusHolder     han...]}
[] in PasteUpMorph>>becomeActiveDuring: {[aBlock value]}
BlockContext>>on:do:
PasteUpMorph>>becomeActiveDuring:
HandMorph>>sendFocusEvent:to:clear:
HandMorph>>sendEvent:focus:clear:
HandMorph>>sendKeyboardEvent:
HandMorph>>handleEvent:
HandMorph>>processEvents
[] in WorldState>>doOneCycleNowFor: {[:h |  ActiveHand := h.  h 
processEvents.  capturingGesture := capturingGest...]}
Array(SequenceableCollection)>>do:
WorldState>>handsDo:
WorldState>>doOneCycleNowFor:
WorldState>>doOneCycleFor:
PasteUpMorph>>doOneCycle
[] in Project class>>spawnNewProcess {[[World doOneCycle.  Processor 
yield.  false] whileFalse.  nil]}
[] in BlockContext>>newProcess {[self value.  Processor terminateActive]}