Sonnet Upgrade Problem

I purchased a Sonnet Encore ST 1ghz upgrade a couple of months ago, I changed over the chip and booted it up, the machine sounded fine but their was no signal going to my monitor, I contacted Sonnet that they recommended I upgraded my fireware, which I tried and it was already upto date, I sent the chip back to Sonnet and received a new one back from them today, problem is that it is doing exactly the same thing.

I have got an Ati Radeon 9000 Pro, do you think that this could be the reason why it's not displaying any picture? or could I need some heatsink compound?

Please help as it's really bugging me now

Oh by the way I have an AGP Powermac G4 running Panther