It happens when web browsing, but I suspect that it happens with any program.
At random times, the screen locks up, moust does respond, but the OS does not refocus when the mouse clicks. Keyboard typing is still recorded but does not display.
Typically I hit the Minimize button on the browser (both IE6 and Mozilla 1.2a) and the screen will go completely black, same resolution, for about 1.5 seconds. Then the desktop returns and the system is back to normal until the next lock up.
This system was recently changed from a Win98se system to a Windows 2K Pro system. Under Win98se this problem did not occur.
Could this point to a problem with the video card? The system's main RAM? or other problems?