If this is a "known" problem, what's known about it? Something in AOLServer? Some OS problem? Some weird date-related problem? Something entirely unrelated to OpenACS? Where has this been discussed before? The discussion over on the AOLServer list by people who know vastly more than I doesn't allude to any prior knowledge of this (
http://news.gmane.org/gmane.comp.web.aolserver)
Seems pretty strange for production sites to suddenly develop problems after running fine for years -- and for other sites apparently not to manifest problems. I've restarted clones of my OpenACS 3.2.5/AOLserver/3.3.1+ad13 sites on a dev box and found no problems with VM or with scheduled procs not firing. I'm not restarting the production sites to see what happens until I learn more about what might be going on.
This is way further into the plumbing than I enjoy venturing, so I certainly hope those who can peer deeply into the stack will let us know what is afoot.