ok, i've now tried various things.
in bios set pci latency to 248, no change.
flicked between pic & agp as being the primary display (even although i have no agp card in my system).
when i did the "$ cat /pric/interrupts" i wasn't in X, when i did it in X i saw the nvidia has IRQ 11.
i did "$ cat /proc/driver/nvidia/agp/host-bridge" and got;
Host Bridge: ALi Corporation M1541
Fast Writes: Not Supported
AGP Rates: 2x 1x
Registers: 0x1b... blah ...000.
still. none of those helped...