Ah I see.
Well I've had temperamental installs with older cards (like RH not liking my old Millenium 4 meg on my old machine...but Mandrake handling it first try).
At that point you have 2 choices, you can either stick with what you have (if you like it and it works...which is all that's important really) or experiment.
(Of course I'm sure if someone else has a solution, they'll speak up as well)
If you decide to experiment with Mandrake (or RH, or any for that matter), I'd suggest trying the install and if the test step crashes...then skip it, boot to commandline and try setting up X from there. That way you'll get actual error messages that you can then find help with (Tons of people here will do their best to help I'm sure.)
If you do it that way, I'd suggest using either Mandrake or RH, but that's just my bias