frustrations

Hi.
Recently my computer has been having some problems that are making me pretty frustrated. One being that occasionally programs will lock up completely - and by this, I mean I cant even terminate it from the task manager. It just stays there frozen no matter what. Ending the process doesn't work either. I have to reset to fix it.

And my USB port suddenly stopped recognizing my devices. It simply says it malfunctioned and when I see what the problem solution is, it just tells me to plug it in again and if that doesn't work, replace it.(which I don't want to do since Im sure its my computer messing up)

Antivirus(AVG) isn't picking up any viruses after a couple scans so its either junk of an antivirus or the problem isn't caused by such.

Im using Windows Vista Home Edition.

Id really be grateful if anyone could offer me insight.

When is the last time you blew th dust out of your computer with a can of compressed air?

Did you make any changes to your computer right before this started? (like install a program or download something)

I cleaned the dust out around 2 months ago, maybe more.

No, I didnt install anything new that I know of, and I didn't download anything besides the usual music and video off youtube(and Ive been doing it for a while so I dont think problems would show up now)

MangoFreak, have you re-opened the case(sounds like lawyer speak) to reseat the components?  It sounds like something may have come loose during the cleaning the process and is not making a permanent connection.