I'm having trouble with your statement that a hard power cycle was
needed to close firefox. If an app in linux can't be killed, then there
is something else going on - bad RAM, overheating perhaps? I would try
logging into the machine via secure shell and taking a look, before
taking such a drastic step.

The kde corruption is most likely the result of the unclean shutdown.
kde is not known for great stability, at least not since the days of kde
3.5.x, so the easiest fix is probably just to remove the kde config
files from your home directory. (I'm guessing.kde* and/or .qt* - but
it's been a few years since I've used kde)

You can verify that the problem is corrupt kde config files by creating
a new account on the machine, then logging in and starting a kde session
under the new account.

You were right on target (.kde folder corruption). Your suggestion got me back
into KDE quite painlessly. I'll have to remember it for future use!

This particular crash, on that website, is very repeatable. I had experienced
it several times under 9.10/Gnome/Firefox, and was curious to see if it would
happen under 9.10/KDE/Firefox.

But I definitely have something else going on. I have experienced other freezes
under 9.10/Gnome - quite random, and not repeatable. My main purpose in
installing KDE is to determine if those freezes correlate to the Gnome
environment. (I've seen them described in 9.10 forums, and on the Mozilla
Firefox forum. I don't believe it's a Firefox problem.) So far, I haven't seen
the "random" freeze in 9.10/KDE/Firefox, but it's too soon to tell.

I don't think it's any kind of hardware problem, though. I still have 8.04 on
another partition, and it's rock-solid. So far, the random freezes correlate
with 9.10/Gnome/Firefox.

Were the person who said they had to reboot because of the freeze?
It may have been someone else, but on that subject, couldn't one bring
up a terminal and just kill the Firefox that was stuck?

In this case, "frozen" described the whole ball of wax, except for the mouse
pointer, and some network activity. No mouse click response, no keyboard
response - including no response to CTRL-ALT-F2 for a text login. Caps lock
wouldn't even change the keyboard light. Power switch wouldn't call up the
shutdown menu. Task bar clock does not update.

Ya, I guess so, I would have gone with the magic switch too.

Ah, interesting, thanks for the feedback. 8.04 is definitely solid - I'm
still running it at work, and won't upgrade until I have a chance to
verify that 10.04 will work well on this particular machine.

With regard to your issue, it's not out of the question that there could
be bugs in 9.10. I'd like to try that problematic URL on my machines, if
you wouldn't mind sharing it.

The video is on this website:

http://www.bayequest.info/2minvideo/83.htm (removing a loose horseshoe)

On my main machine, it reliably freezes up in both 9.10/Gnome/Firefox, and
9.10/KDE/Firefox. Works fine in 8.04/Gnome/Firefox. I should try it on my
other machine, which has an Nvidia card.

Earlier this evening, I experienced two of my "random" freezes under 9.10/KDE.
So it wasn't Gnome, after all.

I'm now reasonably confident that it's a persistent bug in 9.10, probably
related to my rather obsolete PC (circa 2004 Dell, with Intel Integrated
Graphics that required special steps to solve the resolution issue.)

And *that* supports my plan to keep my 8.04 installation as is, and replace the
unstable 9.10 installation with 10.04.

I've had a bit of experience running multiple desktop environments, and my best
advice about mixing and matching is, don't do it. If you want to try KDE, I
suggest installing a second hard drive and using it for KDE. No doubt you are
going to hear from a lot of people who will say it worked fine for them, but
starting with 8.04, every time I've installed multiple desktops, I eventually
had conflicts between them. Something always got hosed up. I finally settled on
Gnome. Ubuntu just doesn't seem to have KDE right, yet.

Boot into Gnome. Delete the .kde folder. Then re-try KDE. It is likely a
setting that got messed up because it did not exit properly. Of course you
will lose all of your customisation and settings, but it should work.

Are you using KDE 4.4 with Karmic? I have found that to be a bad mix. If it
is just KDE 4.3 then it should be stable.

Just out of curiosity, did you first try alt + sysrq + REISUB ? This generally
saves me from hard rebooting.

No - never heard of "alt + sysrq + REISUB", actually. I will give it a try next
time. (But I suspect that the keyboard handler is frozen, too.)

For an expalnation see:
kember.net/.../reisub-the-gentle-linux-restart

The typical keypress is Right-Alt + SysReq + K. It should kill X and bring
you back to login. This replaced Ctrl + Alt + Backspace. Ctrl + alt + delete
typically does not help in Kubuntu. If you just want to kill a frozen
application use: Alt + F2 then type xkill & press enter. You will get a
skull and cross bones cursor icon. Click it on the frozen window (but not
your desktop!).

Thanks for the link - and for your earlier recommendation about deleting the
".kde" folder (which did the trick). (My KDE is 4.3, by the way.)

Since then, I've had a couple of my "random" freezes under KDE. So that lets
Gnome off the hook as a possible cause. (Haven't tried REISUB yet - but chances
are I'll get a chance before the day is out.)

That's probably the end of my efforts in 9.10 for now. I've got a rock-solid
8.04 installation in another partition, and plan to wipe the 9.10 partition in
favor of 10.04 soon.

It's worth a shot... You push all the caps one at a time while holding dow the
alt and sysrq. I should mention you still may have to push the power button,
but your OS should be safely out of harms way at that point. In reality, it
should reboot on its own, but mine tend to hang. The first R switches your
keyboard out of raw mode, e & i are sigterm (kill -15) and sigkill (kill -9), s
& u sync and mount filesystems as read only, and b should initiate a reboot.
You can swap the b for the letter O if you want to try to shut it down instead.

I just had one of my "random" freezes - which gave me the chance to try the
Alt + SysReq + R E I S U B
sequence. Works as advertised!