the problem may be that u have one processor but a chipset that support 2 processor o plus. when you install mandrake seems that it recognize this kind of chipset and install a kernel with APIC feature by default, thing that red hat don't do.
in my sistem the driver worked with redhat but dont with mandrake. so i realize that wasn't a hardware or card problem but in the kernel
the kernel enables APIC even if is disabilited by bios.
the only way is change the kernel of mandrake. look with a terminal with the command uname-a what kind of kernel you're running. IF u find something like that 2.4.21-0.13mdk-smp , you are running a kernel with APIC enabled which seems to crash X. may be is a normal kernel 2.4.21-0.13mdk( without smp, simmetric multiprocessor) but also with the feature APIC enabled. I think that mandrake does this.
- recompile that kernel(bla bla bla)
-install a new kernel by mandrake cd's hoping that it don't have APIC enabled (may be not a solution)
- change distribuition installing redhat9 kernel 2.4.20-8 that seems to work because it has APIC disabled by default
try to solve this kind of problem in linux (that are frequent) means to know a little how the system works, it's not so simple but the documentation is evrywhere, just need a little time to learn and understand.
and realize that this solution may not work for u for reasons that i cant know