1. I have a live knoppix DVD (see bottom of summary for version). Sometimes,
after booting the DVD, the system goes wrong and becomes unusable.

When this happened recently, the resulting effects were as follows:

a) When I clicked on the KMenu icon at the far left of the Desktop Panel (along
the bottom), it didn't fetch up the menu, but caused the whole Panel to flicker
once. The same happened every subsequent time I clicked this icon.

b) I could still use a terminal (LXTerminal) but COULDN'T RUN important commands
like man, kate, or shutdown. I got the following error messages:

$ kate
/usr/bin/kate: /usr/bin/kate: cannot execute binary file
$ shutdown
bash: /sbin/shutdown: cannot execute binary file

So the system had been rendered unusable.

Main Question:

Please could you tell me what is going wrong, and how to fix it. As a temporary
get-round, can I perform a re-login or X Window restart or something else that
will put it back to normal?

I'm about to do some repartitioning on my hard drive using gparted on the live
knoppix DVD, and want to be sure that knoppix isn't going to throw a wobbler
while the repartitioning is taking place!

2. I believe the release of the DVD is given by its filename (as shown in
file manager), namely
/media/sr0/KNOPPIX_V7.0.2DVD-2012-05-30-EN.iso .

I have also installed this DVD onto my hard drive, and it shows up as distro
7.0.2, kernel release 3.3.7.

It works fine on the hard drive.

Full Details:

1. The following describes what I had been doing shortly after booting the DVD,
just before it went wrong.

My hard drive is /dev/sda6, and I think I had just mounted it on /media/sda6
so that I could test opening a file on there.

I opened pcmanfm, displayed my home directory on /media/sda6, then
double-clicked on a text file to open it. Nothing happened, so I double-clicked
on it again, and still nothing happened.

Then I noticed that pcmanfm was setup to "Open files with SINGLE click". So
surely the file would have been opened at least once.

I can't remember EXACTLY what I did next in pcmanfm (if anything), but the
result was that pcmanfm exited, I think without me asking it to.

At this point, the system stopped working properly. The problems were as I've
described in the Summary above, ie Desktop Panel flickers when KMenu icon
clicked, and not able to run commands from a terminal.

2. It takes an age to boot the live Knoppix DVD (about 3 minutes) so I don't
want to have to do that every time it goes wrong.

I had the Panel flicker fault (when clicking the KMenu icon) once before, but
on that occasion it was caused by something else. I think I may have been
trying to switch to another Work-space or something, when it happened.

3. In case it's relevant, when I currently boot the DVD, the metacity X window
manager is in place at the end of the boot.

4. While the DVD was booting today, I saw the following on the screen (I don't
know if it's always there). I'm sorry I only caught SOME details of it (the
"..." below are what I can't recall):

"The graphical subsystem could not be started or terminated unexpectedly.
knoppix ... =radeon ...

Then the boot continued (after a pause?). When the boot finished, THE SYSTEM
BEHAVED THIS TIME. For example, when I double-clicked on a text file in pcmanfm,
two instances of leafpad duly opened the file.