If you run Virtual PC on your Mac, it’s easy to forget that you’re actually running a Windows machine, albeit in a weird, simulated way. And because Virtual PC allows you to save your virtual PC’s state, it’s easy to, in essence, never turn the PC off.
This means that it’s also easy to forget that Windows PCs accumulate internal cruft at an unusual rate, and benefit from a rebooting every once in a while. Today I realized that my virtual PC hadn’t been rebooted in about two years (two years, mind you, of occassional 5 minute usage here and there; it’s been dormant most of the time). Things were starting to get wonkly — applications not starting up, Windows Explorer behaving weirdly.
So I rebooted it.
And everything is fine now.
Moral: even simulated Windows machines need a kick every now and again.