Yes, the problems identified in the screenshots have disappeared since I changed the Mobo.
I've started looking at OC'ing the card/system, but 3dmark06 will not complete a test with the card or system even remotely above stock speeds. Also, playing COD2 and Far Cry is a pretty crashy experience with the card OC'd, but fine with everything at stock.
This isn't in itself necessarily a problem, as the card is way more powerful than anything I've had before, and I only game at 1280 x 1024 anyway, but it does seem strange that I can't budge it stably even a little above stock.
With Coolbits installed, and using the Nvidia panel to test the OC, I can get the core to nearly 500 but the memory doesn't really like going any higher, so there might be something in the memory points above.
I suppose the XFX card is already OC'd though, and as long as it's stable at stock then I'm happy enough and can't really argue it's an RMA, especially given the price I paid for it.
Just to check it out, I'll run the benchies again but with the memory underclocked and report back what happens.