hi steve,
1. nope, it never gets stuck.
2. i never run only a few mac applications. i usually have tons and tons of applications / windows open.
it just happened again. i pasted and got stale clipboard info. i <cmd>-<tab>'d back to Mac Firefox (where i'd copied from), then immediatedly <cmd>-<tab>'d back to my XP vm and pasted correct clipboard info. i grabbed the vmusr.beej.olog file just after and am attaching it.
don't worry about my diagnosing this issue being disruptive to my work. the bug is more disruptive and we wouldn't be having this conversation if i weren't keenly interested in getting it fixed 
my guess is that if this vmusr log doesn't help, we're going to need to get a custom build of vmtools with more logging, or something.
thanks for looking into this!
marc