That is typically an issue with bad memory. Could be a virus or badly coded program that is causing the issue. Some programs like Alcohol120%, have been known to cause issues. To start, grab a copy of Memtest86+ (the one from the .org site, not .com site). Burn the ISO to a CD, boot from the disc and let the test loop for 24hrs or until it shows failures. If after 24hrs there are no errors, you can be 95% assured that the memory is OK, and this is probably a software/virus issue and not failed memory.