I've looked through here, through the Boinc forums, and Googled, but I
can't find any solutions to this problem:

I've been running Boinc for months without issues until I tried out
the Windows Vista previews. Boinc seems to run fine except that it
won't stop processing work units, nor unload from memory when I'm
active on the computer.

I double checked the preferences and they are correctly set to run
only when the computer is idle. But for some reason it refuses to stop
running. Boinc is version 5.4.11, the current release.

This isn't a problem for my work computers where they're not under
heavy loads, but at home I do a lot of testing and and I really need
to free up all resources and memory when evaluating some intense
programs.

Has anyone else had a problem with Boinc and Vista like this?