For sometime I have been unable to do 'Update Squeak' from the latest trunk image on Mac, no matter which VM I was running on.
I had not been able to devote any time to the problem until now and I reported the issue: <http://bugs.squeak.org/view.php?id=7574>. The problem turns out to have been caused by an incorrect SqueakV41.sources file.

By luck while looking at where Syntax Error might be generated in order to place a self halt for further debugging, I got a warning saying that my SqueakV41.sources file was missing something, and suggested making sure it was treated as a binary file for initially expanding. I re-downloaded a new ftp://ftp.squeak.org/SqueakV41.sources.gz, expanded it normally and did a diff between what I had from a previous download and the newly expanded one. They were significantly different. Somewhere along the line I had downloaded the SqueakV41.sources file and had been treating it as the master on my system. Alas, there have been more than one version of SqueakV41.sources available for download with exactly the same name and the previously downloaded one did not allow for Update Squeak to work.

Using the newly downloaded SqueakV41.sources allowed the Update Squeak to proceed normally.
This bug should be set to 'Resolved'.

I am mentioning this here in order to potentially save someone else some grief.
Care needs to taken that more than one version of the SqueakV41.sources are not floating around causing weird things to occur.

Ken G. Brown