Def not PC power supply - quite likely not video card.

Resolution and refresh rate combos can do strange things especially on certain CRTs.

Just yesterday we pulled a 9month old (non-refurb) Mitsubishi off the floor due to it behvaing very strangely in 1600x and 1024x (1280x ran flawlessly) in any refresh over 60 - and who wants to run that - ack.

Just things you can try to narrow down the problems and troubleshoot.