I have a Chaintech FX5200 w/128MB and have a very similiar problem. I been researching this and have found that agpgart is not supported. I'm still looking for a fix.
If you look through your syslog through Mandrake Control Center you may find the same error. This sort of ticks me. I bought a NVIDIA for the support they have compared to ATI. I hope they will fix this soon. Another video card is starting to look good.
I guess there are more people in the boat with me. Keep bailing, please.