In an updated 5923 image on windoz. Nothing loaded except the basics.
Select open from the world menu, select morphic project. Enter the new
project, return to top project. The  bottom three tabs are red boxed
with the yellow cross hatch and I get this walkback.

Something weird here, I can't believe this hasn't been seen yet. I must
be doing something but I can;t figure out what.

2 June 2004 7:58:40 pm

VM: Win32 - a SmalltalkImage
Image: Squeak3.7beta [latest update: #5923]

SecurityManager state:
Restricted: false
FileAccess: true
SocketAccess: true
Working Dir C:\downloads\Squeak\5905
Trusted Dir C:\downloads\Squeak\5905\frank
Untrusted Dir C:\My Squeak\%USERNAME%

UndefinedObject(Object)>>error:
	Receiver: nil
	Arguments and temporary variables: 
		aString: 	'MessageNotUnderstood: UndefinedObject>>+'
	Receiver's instance variables: 
nil

[] in WorldState>>displayWorldSafely: {[:err :rcvr |  errCtx :=
thisContext.  [errCtx := errCtx sender.  [errCtx no...]}
	Arguments and temporary variables: 
		aWorld: 	a PasteUpMorph(4073) [world]
		err: 	'MessageNotUnderstood: UndefinedObject>>+'
		rcvr: 	nil
		errCtx: 	TextMorph>>privateMoveBy:
		errMorph: 	a TextMorph(432)

BlockContext>>valueWithPossibleArgs:
	Receiver: [] in WorldState>>displayWorldSafely: {[:err :rcvr |  errCtx
:= thisContext.  [errCtx := e...etc...
	Arguments and temporary variables: 
		anArray: 	#('MessageNotUnderstood: UndefinedObject>>+' nil)
	Receiver's instance variables: 
		sender: 	BlockContext>>valueWithPossibleArgs:
		pc: 	113
		stackp: 	0
		nargs: 	2
		startpc: 	66
		home: 	WorldState>>displayWorldSafely:

[] in BlockContext>>ifError: {[:ex | errorHandlerBlock
valueWithPossibleArgs: {ex description. ex receiver}]}
	Arguments and temporary variables: 
		errorHandlerBlock: 	[] in WorldState>>displayWorldSafely: {[:err :rcvr
|  errCtx...etc...
		ex: 	MessageNotUnderstood: UndefinedObject>>+


--- The full stack ---
UndefinedObject(Object)>>error:
[] in WorldState>>displayWorldSafely: {[:err :rcvr |  errCtx :=
thisContext.  [errCtx := errCtx sender.  [errCtx no...]}
BlockContext>>valueWithPossibleArgs:
[] in BlockContext>>ifError: {[:ex | errorHandlerBlock
valueWithPossibleArgs: {ex description. ex receiver}]}
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
BlockContext>>valueWithPossibleArgs:
[] in MethodContext(ContextPart)>>handleSignal: {[(self tempAt: 2)  
valueWithPossibleArgs: {exception}]}
BlockContext>>ensure:
MethodContext(ContextPart)>>handleSignal:
MessageNotUnderstood(Exception)>>signal
UndefinedObject(Object)>>doesNotUnderstand: #+
NewParagraph>>moveBy:
TextMorph>>privateMoveBy:
TextMorph(Morph)>>privateFullMoveBy:
FlapTab(Morph)>>privateFullMoveBy:
FlapTab(Morph)>>position:
FlapTab(Morph)>>bottom:
FlapTab>>positionObject:atEdgeOf:
FlapTab>>fitOnScreen
FlapTab>>layoutChanged
FlapTab(Morph)>>extent:
[] in FlapTab>>fitContents {[self extent: submorphs first extent + (2 *
self borderWidth) + (8 @ -1).  s...]}
FlapTab>>ifVertical:ifHorizontal:
FlapTab>>fitContents
FlapTab(ReferenceMorph)>>layoutChanged
FlapTab>>layoutChanged
TextMorph(Morph)>>layoutChanged
TextMorph(Morph)>>extent:
TextMorph>>fit
TextMorph>>paragraph
TextMorph>>drawOn:
FormCanvas(Canvas)>>draw:
FormCanvas(Canvas)>>drawMorph:
[] in TextMorph(Morph)>>fullDrawOn: {[(aCanvas isVisible: self bounds)  
ifTrue: [aCanvas drawMorph: self].  self...]}
FormCanvas>>roundCornersOf:in:during:
FormCanvas(Canvas)>>roundCornersOf:during:
TextMorph(Morph)>>fullDrawOn:
FormCanvas(Canvas)>>fullDraw:
FormCanvas(Canvas)>>fullDrawMorph:
[] in FlapTab(Morph)>>drawSubmorphsOn: {[:m | canvas fullDrawMorph: m]}
Array(SequenceableCollection)>>reverseDo:
[] in FlapTab(Morph)>>drawSubmorphsOn: {[:canvas | submorphs  
reverseDo: [:m | canvas fullDrawMorph: m]]}
FlapTab(Morph)>>drawSubmorphsOn:
[] in FlapTab(Morph)>>fullDrawOn: {[(aCanvas isVisible: self bounds)  
ifTrue: [aCanvas drawMorph: self].  self...]}
CornerRounder
class>>roundCornersOf:on:in:displayBlock:borderWidth:corners:
FormCanvas>>roundCornersOf:in:during:
FormCanvas(Canvas)>>roundCornersOf:during:
FlapTab(Morph)>>fullDrawOn:
FormCanvas(Canvas)>>fullDraw:
FormCanvas(Canvas)>>fullDrawMorph:
[] in WorldState>>drawWorld:submorphs:invalidAreasOn: {[:r |  rectToFill
:= r.  i := 1.  [rectToFill isNil   or: [i > n]]   whileFa...]}
Rectangle>>allAreasOutsideList:startingAt:do:
Rectangle>>allAreasOutsideList:do:
[] in WorldState>>drawWorld:submorphs:invalidAreasOn: {[:dirtyRect |
dirtyRect   allAreasOutsideList: validList   do: [:r |     rec...]}
Array(SequenceableCollection)>>do:
WorldState>>drawWorld:submorphs:invalidAreasOn:
[] in WorldState>>displayWorld:submorphs: {[worldDamageRects := self    
drawWorld: aWorld     submorphs: submorphs    ...]}
...etc...