Windows 7: I type the screen goes black

I just had the strangest problem. Typing more then 3 characters makes the screen go black and a few seconds later it recovers but it reoccurs. I noted no hard disk activity on the monitor.
Obviously better now- it just make me worry there is a real problem. Its a monitor (integrate in the screen) computer. Windows 7 Pro Japanese. Still getting lockups but I don't worry about those- sometimes when background computer activity starts.