Programs/Task Manager Will Not Open

After my computer has been running for an unknown period of time, all unopened programs will not open. As I try to open any program (or the task manager) the cursor turns into an hour glass for a moment, and then nothing happens. I have ran CCleaner, AD-Aware SE, Microsoft AntiSpyware, Power Defrag, Spybot - Search & Destroy and the problem still happens. When at first I boot my computer, everything runs normally, and I have not actually witnessed the problem take place (that I am aware of). As I cannot open any programs that are not already running, NOR the task manager after the error occurs; I opened and left the task manager running before the error. I was able to identify the svchost.exe was using 99%-100% CPU, and I could not kill the process.

Any suggestions?

 

What kind of antivirus do you use? I've seen several security software cause hangs like this (though usually a lot more consistantly).

Any recent driver updates? Any bangs in device manager?

 

I have been using Symantec AntiVirus because it is mandatory to the school I am attending. I have not been able to recall any new updates installed lately, and everything in the device manager seems okay.