SOLUTION:

Ok I went for the inelegant option of installing a new instance of SuSE
9.1 on a seperate partition. Updated the system (including the kernel)
with YOU. I did NOT install the fetchnvidia SUSE driver. Instead I
installed version 61111 of the nvidia driver from nvidia.com
I got an error about rivafb being installed as a kernel module. This
module is never loaded so there is no problem. I ran sax2 -m 0=nvidia
and set up my monitor and screen resolution but did NOT configure 3D
support in sax2. I then init 5 and get back to KDE. Run glxgears and get
7100 FPS. Rock on! YOU must have buggered something. I've now migrated
to the new 9.1 and everything is much better. Some other minor problems
I've had have also gone away.

Interesting second problem though which other people may find helpful:
- Every time I ran a 3D app the system would hang for long periods. The
app (e.g. unreal 2004 or neverball) would still run in the background
(sometimes heard audio but got a static image). UT2004 utter unplayable/
Googled a bit for things like "nvidia SuSE 3D hang": nothing. Then I
came across a post on memory leaks and someone mentioned overheating GFX
cards: BING! My GFX card fan had died a while ago and I'd replaced it
with a passive Zalman heatsink. Card was overheating. Placed a fan next
to the heatsink and turned up the cases's cooling (4 fans with variable
RPM) to max and now I have a silky smooth system! UT2004 is playable on
1600x1200 with all GFX settings on their highest values! I prefer the
res a little lower though as it is slightly smoother.

Hope all this helps others.