I know this topic is fairly old, but I found it while I was trying to find an answer, as I was having the exact same problem. Gbhall's response helped me figure out the problem. I remembered that I had something plugged into my USB that I did not really have set up properly. When I plugged it in a while back, it said to search for a driver to install it, and I just said No because I was too impatient, and wanted to get to doing other things on the computer. Once I unplugged it, all the problems were fixed.
I suggest looking at the front and back of your computer, and look for anything that's plugged in that could be causing a problem. Even try unhooking everything aside from your mouse, and see if it does anything. If it isn't fixed, then you know it isn't any of the random hardware. If it is fixed, then it is a simple process of elimination.