I traced it down to this method, where fileName = 'C:\Squeak 
4.1\package-cache\LayeredProtocol
-rww.2.mcz' and writeMode = true.


StandardFileStream>>#open: fileName forWrite: writeMode
	"Open the file with the given name. If writeMode is true, allow writing, 
otherwise open the file in read-only mode."
	"Changed to do a GC and retry before failing ar 3/21/98 17:25"
	| f |
	f := fileName asVmPathName.
	fileID := StandardFileStream retryWithGC:[self primOpen: f writable: 
writeMode]
					until:[:id| id notNil]
					forFileNamed: fileName.
	fileID ifNil: [^ nil].  "allows sender to detect failure"

The call to #primOpen:writable: is failing silently and returning nil.  I 
have no file by this name on my file system.

This is preventing me from publishing anything.  Here is the strange 
thing...I can publish my other project.

Thanks,
Rob