Unable To Load (initialize) IE Due To Insufficient Resources - MBR

I am constantly connected to the internet via the university's network, run AVG 7.1 free, spybot s&d and its tea timer, and ad-aware se personal, all with updated definitions. I run an ewido online scan once a week, but don't keep it installed since it causes my computer to boot much more slowly. I also have the most current windows updates, except WMPlayer 10, and .Net 2.0 because it seems unnecessary. Well, back to the problem. I was talking to my friend on AIM, when I got the message "The connection to the service was lost" and had options to try and reconnect, etc. I tried to load IE, but it gave me some error along the lines on "Unable to load (initialize?) IE due to insufficient resources." I have a gig of ram, 3.0 GHZ P4, 120 Gig of hdd space, about 80 gig free, and run CCleaner about twice a week.

Anyway, I've been clean according to those 3 programs I use frequently, but after I got kicked off AIM and IE wouldnt load, my favorites were empty, programs wouldnt load, i couldnt shut down, etc. So I hit the reset button. When rebooted, the BIOS screen showed, and stayed for along time which it never does. Then, it kind of froze. As illogical as this seems, I just hit the switch on the back of the powersupply and waited about 2 minutes. All of my fans are clear of dust and in working operation (GPU, CPU, and PSU). I havent installed or removed any hardware / software recently, etc. So when I restarted, I rebooted into "safe mode with network support" and ran Spybot, Adaware, AVG7.1 and Ewido online scan. None reported anything outstanding, but AVG notes that read errors occured for the MBR and boot sector. Ewido found "spyware.chitika" which it removed. I rebooted and am currently in "safe mode with networking" just to be safe, but my question is: what could have caused this? and how can I fix my MBR? Thanks for any suggestions. I have a final paper that I need to finish before friday!