Question : Windows 7 Freezes when screen saver is on

I will leave my PC with Windows 7 running.  The screen saver will run.  After I come back from 3 hours, the screen is black and I need to reboot the PC.  After the rebooting the PC, Windows 7 resumes, however, all applications and the OS are running very slow.  What is causing this and how can I resolve it?

Answer : Windows 7 Freezes when screen saver is on

Try installing the new Windows 7 RC.
http://technet.microsoft.com/en-us/evalcenter/dd353205.aspx