Glad to see I'm not the only one with this problem. I've tried this hotfix, but it apparently does not apply to my system (so says the message when I try to install).

I'm on a Dell XPS 630, with Vista Home Premium. Both Firefox and IE eventually slow down and become unable to connect to any website. Any external programs that connect to the Net function fine. Other programs tend to hang after this happens when I try to open them, and I'm normally unable to end task both browsers (also reaching the shutdown/restart screen can take anywhere from a few moments to a full half hour).

The period of time before the slowdown and inablity to connect starts to occur can vary from five minutes to a few hours.

I'm pretty convinced it's Vista as it happened without any thirdparty firewall or anti-virus programs running the first time around.

I'd really hope that Microsoft will address this highly inconvient bug.