Hello. My first thought would be that something is wrong with the RAM in your system. Try running a bootable memtest86 (http://www.memtest86.com/
) test for a few hours and see if you get any errors.
If you have not changed the configuration of your system during this period, or installed updates to your software, I personally think this points more to a hardware issue.
Also, have you checked the hard drive(s) for errors?