well, tsubasa is a bit fast when it comes to KT400 mobos
no, your problem is not the same problem that we have, but is in fact the problem that gdb has...
but you mentioned that it had worked before rebooting...
that indicated that the module doesn't load at boot time.
most of the time that comes from shutting down X the wrong way.
in mdk9.1 you should use /etc/init.d/dm stop as root in CTRL-ALT-F1 and restarting it after installation and modification the same way.
do not install in failsafe mode or any other.
there are lots of people with mdk9.1 that can make this work correctly.
If you can get it to work with mdk9.0 you sure as hell can get it to work with mdk9.1.
also try running ldconfig as root,
there have also been known problems with the GLX (conflicting versions, mesa or XFree86 ) so you should check /var/log/messages as well.
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