Windows Explorer Crashing/Windows Defender Errors

I have an HP laptop (I've posted all of my specs), that's having quite a few issues. These problems have been going on for a few days now. First off, when I turn my computer on, I get the MSASCui.exe error indicating that something screwy is happening with Windows Defender.

http://img31.imageshack.us/img31/2283/msascuierrormessage.jpg
(Not my image, but this is the exact error message I got)

Now everything is acting extremely slugish and task manager has stopped working. So, I shut everything down and start up again. Error message pops up again and everything is still slow. It takes at least 20 minutes for it to fully load the desktop. And now Windows Explorer crashes every time I attempt to open an explorer window (such as computer or control panel).

I don't think it's a virus, as I have AVG and Spybot and scan daily. I haven`t downloaded a thing in a week. I am running the Windows Malicious Software Removal Tool's scan, as Malwarebytes' Anti-Malware scan and SUPERAntiSpyware's scan. I've done an AVG scan, and Spybot scan, fixed registry errors with CCleaner and disabled windows defender...

Nothing I've tried works. Any ideas are appreciated.