Comment 17 for bug 710144

Almost. The process which logs you in to your X session (I guess it is kdm, but I'm not entirely sure) calls the Xsession script which creates your actual session. That script expects either one or zero parameters: The name of the session to use. If no parameter is given, it assumes you want to use the special session with the name "default" which falls back to whatever the default session is on your system.

Now the bug is that, due to some misconfiguration, your session name is invalid. Afterwards, instead of calling Xsession without any parameter, it is still called with a single parameter: The empty string "". Xsession tries to map this string to a session name, gets confused, throws up a nasty xdialog and falls back to default.

So we've got two bugs here:
* Xsession doesn't handle an empty session string (which can mean only "default" IMHO) gracefully.
* Whoever calls Xsession should not use an empty string but leave the first parameter if the user wants the default session. I think the bug is in kdm, but I'm not sure so I don't know where to report it upstream.

The (now tested) patch I posted before fixes Xsession to handle kdm's (?) odd view of a default session.