I encountered the same error...here are some more details:

1 August 2002 10:40:41 am

VM: Win32 - Squeak3.2gamma of 12 January 2002 [latest update: #4879]
Image: Squeak3.2 [latest update: #4935]

UndefinedObject(Object)>>error:
	Receiver: nil
	Arguments and temporary variables: 
		aString: 	'UndefinedObjects are not indexable'
	Receiver's instance variables: 
nil

UndefinedObject(Object)>>at:
	Receiver: nil
	Arguments and temporary variables: 
		index: 	7
	Receiver's instance variables: 
nil

MaRepositoryControllerFacade>>anchorRequest
	Receiver: a MaRepositoryControllerFacade 
	Arguments and temporary variables: 

	Receiver's instance variables: 
		link: 	a MaLocalServerLink 
		session: 	a MagmaSession 
		requestPrototypes: 	nil

MaRepositoryControllerFacade>>anchorBuffer
	Receiver: a MaRepositoryControllerFacade 
	Arguments and temporary variables: 

	Receiver's instance variables: 
		link: 	a MaLocalServerLink 
		session: 	a MagmaSession 
		requestPrototypes: 	nil

--- The rest of the stack ---
MagmaSession>>anchorBuffer
MagmaSession>>anchor
MagmaSession>>root:
MagmaRepositoryController class>>create:root:
UndefinedObject>>DoIt
...

> -----Original Message-----
> From: squeak-dev-admin at lists.squeakfoundation.org
> [mailto:squeak-dev-admin at lists.squeakfoundation.org] On 
> Behalf Of Hernan Wilkinson
> Sent: Thursday, August 01, 2002 9:46 AM
> To: squeak-dev at lists.squeakfoundation.org
> Subject: [Magma] Error creating a Repository
> 
> 
> Hi,
>   I just donwloaded Magma and installed it.
>   I tried to create a repository just as the example
> shows,
> 
> MagmaRepositoryController
>     create: 'c:\temp\myRepository.magma'
>     root: Dictionary new
> 
> but I get "UndefinedObjects are not indexables"
> becuase requestPrototypes is nil...
> 
> Am I missing something? Do I need to do something else
> before creating a repository?
> 
> Thanks, Hernan.