I just installed Snapshot Pro for on WPMU. I've tried running it twice and both times I'm getting an error
Error 500 - Internal Server Error
An error was encountered while processing your request. Typically this is a temporary condition. Please contact the web site owner for further assistance.
It progresses almost to the bottom, but it kills over at 60% on "Files: plugins".
My MU site is really, really small as I've only been tinkering and haven't really made anything public yet.