Welcome to HWC.
Have you tried using different PSU connectors? How about disconnecting all other peripherals (CD-ROMs etc) and just have the motherboard and the 9500 connected?
Can you tell me what revision your 9500 PCB is please? Should say so in white writing in the top left hand corner on the front of the card (if it is one of the red ATi reference designs - if it is black then don't worry about it)
94200-XX, where "XX" is the revision.
Opteron email@example.comGHz (stock HS/fan), Asus A8N-SLI SE (passive NB), 1.5GB RAM (2:3:2:5, 2T), WD Raptor 740GD 74GB, Maxtor DM10 300GB, Asus EN7600GT SILENT@???, M-Audio Revo 7.1, Nebula DigiTV, Dell 2005FPW, Enermax 431W Active.