Hi there, well you have me stumped, I haven't experienced anything like what you are describing!
I am up to date with all my systems, IE7 Beta, MSN 8 Beta, all VAIO updates done on a regular basis. Have got the validation stuff etc,,,
I use IE, but use Firefox when felling a bit paranoid, but other than that am running spyware blaster, ad aware, avg, avast, norton and symantec, windows defender and also spybot,,,, also being behing a wireless router gives a hardware fiewall effectivley.
Back to your snag though, I'd say, download and run crap cleaner,,, use the "scan for issues" option and see if it can find some hidden issues...
this may actually resolve any snags since you updated as something may have been left behind,
Another thing you can do if all else fails is return to a "restore point" prior to you last critical update and do a clean install of the updates paying close attention to re-starting correctly.
Let us know how you get on, any snags, get back and we can scratch our heads together on this one.