What DirectX version do you have?

6.1a - I believe this is the version that comes standard with Win98SE

You could try Omega Drivers, it helped me when I was trying to use very unusual AGP card with mobile Radeon 9600 chip under W98
EDIT: nope, they probably work only with Radeon cards 🙁

Maybe try some older drivers, like these http://vogonsdrivers.com/getfile.php?fileid=341&menustate=0

Or update DirectX.

Hello J!

When i installed a Rage 128 based card to one of my Pentium II Windows 98SE computer, i encountered the same issues.
This was in the beginning of this year, so my information about this not 100% correct, but there is the solution:
1. Remove the current card driver.
2. Click on Add New Hardware in Control Panel.
I assume you downloaded the file named WMER1284137192.EXE, which extracted files into a specific folder.
3. Add manually the corresponding .inf file.
4. You see two drivers with exactly same name. One of them has -If i recall correctly- workstation card names. This was the version that windows installed, which doesn't have Direct3D support.
5. Install the other driver.
If you did everything right, you can test Direct3D, run games and benchmarks.

I hope i could help you.
Joe

All,
Thanks so much for the help and suggestions. I'm working through them sequentially. First thing I did was install a newer version of DirectX straight of the original Call of Duty CD. I've now got DX 9.0b (which I'm surprised works on this card), but things seem to work now, I can run 3Dmark 99 (905 and 1406 CPU for those curious). Things seem stable for now... Joe if I run into further issues I'll follow your process.
Thanks again,
J