Ok, not really anything to finally solve your problem:
I have a ti4200 with the same problem - look at
A friend told me it's probably SuSe's fault, but...
However, I managed to get higher resolutions. I'm not quite sure why that is, but maybe it's because I changed the monitor settings (after I had installed the latest driver Linux somehow "forgot" my monitor). Both settings should nevertheless have allowed resolutions of 1600 and higher.
Anyway, after a reboot I could use higher resolutions but in 1400x1050 I get no more than 75Hz refresh rate - not nice on a 22" high contrast screen.
I'm going to try a few things out right now, then come back and tell you what I found out... unless someone else knows an answer to the problem and is nice enough to tell us about it.