OK, you motivated me to find a solution to my problem. Let's see if the same solution works for you.
Edit your /usr/kde/3.5/share/config/kdm/kdmrc
See if you have a line like:
- Code: Select all
Uncomment that line, then close everything down and restart your X-server (<ctrl><alt><backspace>).
Let me know if this works for ATI cards also.