i have/had the same problem you describe w/ suse 8.2 and gforce4 mx 440
your kdm.log file has in it stuff like:
(EE) [GLX]: Failed to add GLX extension (NVIDIA XFree86 driver not found)
Xlib: extension "GLX" missing on display ":0.0".
Xlib: extension "GLX" missing on display ":0.0"
this is the same in mine when using the default kdm "boot" to X
until the code gets fixed! here is the workaround i am using
boot into "safe" mode, login as yourself and startx
i posted a thread about this at:
let me know what happens with the "workaround"