I have kde4 installed, but still want to have kde3 as my default desktop. The default setting in kdm is "Default (previous)", where I'd assume that kdm starts the last session I had, which usually is kde3. Though this doesn't work, it always starts kde4 if I don't explicitely select kde3 in the session selection.
Hanno, can you please check if this still happens with 4.1.3? I haven't hit this bug.
I have looked into it a bit and I think I know the cause: I'm using pam_mount to mount my homedir. Seems that kdm reads out the .dmrc before the pam authentication, but writes it back after it. Though it always uses the .dmrc from the unmounted home mountpoint and always writes it back. I'll try to investigate this further and report something upstream.
pretty old bug, please test with latest kdm (4.3.1 || 4.3.3).