Visual Studio 2005 Service Pack 1 has been released. Get it here. Note that if you are installing the thing on Vista you should explicitly use "Run As Administrator" assuming UAC is turned on (yes, I am back on UAC). Yet, it doesn't work for me. Perhaps there is a problem with SP1 beta which I installed before?
BTW, Isn't this a perfect descriptive message?
There is also a link to Visual Studio 2005 SP1 Update for Windows Vista Beta (I guess the update is beta and not for Vista Beta) but it isn't yet functional.
UPDATE (16.12.2006): Yes, it was SP1 beta. Andrej has posted SP1 beta uninstall instructions here.