What CPU is your system using and which version of Windows? Also is the operating system 32 bit or 64 bit? I will be happy to help you out if you can provide me with a little more information about the system.
My first recommendation would be to run a full system scan on your system for viruses using ClamWin Anti Virus to ensure it's not a virus of sorts causing you the problems. I have provided a link below to where you can install the software.
http://www.clamwin.com/content/view/18/46/