I have a Dell 1626HT CRT Monitor (21") attached to a Dell GX400 tower running Windows 2000. I had shut the computer down for a few hours. When I turned it back on, the monitor display had a semi-hourglass shape (concave at the middle on both sides). Device manager tells me my video card (nVIDIA gFORCE2 GTS) and my monitor are working correctly. The Dell Diagnostic software did not find anything wrong with my display. Can anyone tell me what's causing this?