Check out kde 3.5x bug reports as this is an old error. I remember it
has something to do with a corrupted file in the user's .kde
directory. This bug was most common when opening a root konq session
from a reg user.
Common fix is to run kpersonalizer to clear away corrupted files, then
resetting the user to preference.
The more aggressive fix it to move .kde to .kde.old.
Try creating a new user and see if this happens again.
Hope this helps,
Kate