power issue

1 year old PC built by me for a client of mine. Client recently replaced power supply. Not immediately after power supply changed but now have the following issue. Power up PC. Power starts up for approx. 3 seconds and then PC powers up again in a continuous loop. I’m suspecting an incompatable power supply. The MB is an ASUS P5B deluxe with an EVGA GeForce 7950 GT 512MB PCI Express powered graphics card. The power supply is an ATX 450 Watt 24 pin with the separate 4 pin connector. Am I on the right track suspecting the power supply.