|If this happened before the new install then I would suspect it is memory issues.|
Google for memtest86 and boot to it and run it for over night. Any errors detected means that you have a bad memory stick.
Another aspect could be that you have some applications trying to run in the background that is causing the problems...If you have low memory issues then this could be the cause of it as well. this program is free and works well in stopping these applications from running in the background or starting at the time you start your computer...(other than security and video, there is no need for programs to be running untill you use them.)
google for these:
Change Is Good