I have a Dell PowerEdge 700 server that keeps locking up on me.

This server is running Windows 2003 server. It’s also running RAS services for dial up connections as well as Apache services for internet access to the server. It randomly locks up so that you cannot connect through dial up or through the internet but I can ping the IP address of the server and it responds back. When I check the server at the console I only have a grey screen and no response to the mouse or keyboard and have to re-power the unit to get it back up. There are also no errors in the event log. Does anyone have any suggestion for a fix?