Note: If you're asking for technical help, please be sure to include all your system info, including operating system, model number, and any other specifics related to the problem.

-have you recently installed any new software?
-replaced any hardware in the computer?
-when was the system components last cleaned (from dust, etc.)?
-noticed any other unusual behavior from the system?

Provide us with as much information as possible, so that we can help you better.