Internet explorer failed....virus??

So i was working on my dell dimension desktop today. one second internet explorer was fine, then bam...it stopped working. i just get the page cant be displayed error. i thought virus for a while, but there are no problems with slowing, my firewall and antivirus both appear fine, and didnt ask for anything unusual. i know the internet connection is still live cuz im using it on this pc, but im stumped. i've power cycled the modem. ran ad-aware and hijack this. nothing unusual.

heres why i still think virus though....the next day, my mcafee antivirus had stopped functioning correctly...wont enable live protection, or start a scan. also, my system restore fails....restored several points from the day before, all the way to 2 months before.

more info...i downloaded (but did not install) internet explorer 7 beta and musicmatch jukebox 8.0 (which was also not installed). my firewall did ask for something (i think it was like WDM or something but i cant remember...i googled it first and it showed up as non malicious microsoft something or other on multiple websites)...

any suggestions would be GREATLY appreciated