AGP port can it damage my card like this?

Hi

I have a Gigabyte Mobo GA-8IG1000MK. Recently my Power Colour Radeon 9800XT card became very distorted in 3D games producing checkerboard patterns plus a lot of other weird patterns. The card was just out of warranty and I never got any response from Power Colour as to if they would help even though I offered to pay them. So I bought a Sapphire X850xt AGP. After installing it all appeared to be OK till I played Myst V, Swat 4 when in an area of the game where water or flashing lights (top of cop cars Swat4) the checkerboard pattern was present again.

ATI standard answer is that the card is faulty return it.

My question is could I have a problem with the AGP port on the mobo? I have an older GeForce 3 Ti 500 card which runs OK on this board and the X850XT is OK in Joint Ops and Pacific Fighters.

Thing is the store where I bought the X850XT is OK with a replacement card, but I don’t want to stick it back into a maybe faulty board.

Anyone have enough tech now how to say if this kind of fault is possible?

Thanks for reading my rant.

Regards
Allan