In an attempt to resolve some other mysterious problems, last night I 
downloaded a fresh Squeak3.2gamma-4857.image and, while I was there, 
the Squeak 3.2.7Beta5 VM (this is all on MacOS X 10.1.2).

I read some file Ins, saved the image, but could not do a file out of 
my modified chgangeSet!

A little poking about showed that

	StandardFileStream new primOpen: 'foobar.cs' writable: true

returns nil, which gets propagated all the way up to 
ChangeSet>>fileOut, where nil fails to understand #header.

Yes, the FilePlugin is loaded, no the disk is not full.  What is 
weird is that at some earlier point I was successfully able to save 
the image under a new name, and even after this failure could 
checkpoint to that image file.

Using the checkpointed image, I restarted with the Squeak 
3.0Alpha21MTCarbon VM, and was able to do the fileout without any 
problems.   3.0Alpha21MTCarbon uses FilePlugin 30 May 2001 (i), 
whereas Squeak 3.2.7Beta5 uses FilePlugin 9 May 2002 (i).

So this looks to me like a VM problem.  Has anyone else seen this?

	Andrew