I'd been wondering if this was just me. Also running Vista 32, get the same problem, and get it with Hammer, too.
I find I get it only about 50/50 on TF2 if I wait about 30 seconds between disconnect from server and quitting the application. I've bugged it to both Valve and Microsoft, as I'm not sure which is causing the error. I'd be interested if anyone knows any fixes.