Thanks, I will keep an eye on the virus scanner.
Just to provide some closure.
1. In the case of world-menu loss in Croquet, it turns out that I was occasionally loading themes for eToys, but not reaching for the root menus right away. See http://lists.squeakfoundation.org/pipermail/squeak-dev/2009-January/133538.h tml 2. For the case of the Pharo image, I believe I was using a 3.10VM. I have been running an image today (Pharo, with Cassou's latest updates, although I am using the "Core" image as a starting point) with VM 3.9.1 . and it has run all afternoon without a glitch - I haven't been coding the fulltime, but I am still impressed, as this is what one expects.
Thanks to all of you who offered helpful advice. And thanks to all Squeak contributors. very nice!
-Cam