Had a serious CPU/RAM bottleneck recently on ubuntu. I recently switched
from mandrake to ubuntu, and I really like it. But I'd really like to know
what caused this, so help me to prevent it from happening in the future

System: PIII Celeron 1.1Ghz, 256meg RAM, nvidia Gf4 128meg vid card.

standard 3d nvidia drivers, obtained via apt-get.

System seems to bottle necked in a major fashion.

Was watching an avi on mplayer using "-vo xv" option, while downloading
stuff with apt-get, and chatting on irc with xchat.

The keyboard stopped accepting input, and the mouse pointer froze. The
movie kept running, so I continued to watch it until the screen saver

Not wishing to force reboot anything, while apt-get might be in the
middle of installing stuff, I went away for 1/2 an hour or so. Came back,
and I could still hear the film going ... but it was jerking, the audio
was cutting in and out, as though mplayer were having difficulty
buffering. And I could the hard drive whirring like it was about to emit

Waited a little longer, then pressed ctrl + alt + backspace. There was no
response so I pressed the force restart on the box.

When the box restarted, it started emitting the machine gun beep noise you
get when you hold a button down on the keyboard. Then it refused to boot,
saying "No keyboard, or non system keyboard present".

Unplugged the box, jiggled the keyboard usb cable a bit at the back.
Plugged it back in. This time the system didn't post, and all I got was
one long beep, followed to short ones.

Unplugged it again, removed the keyboard usb plug from the box, and
switched it on again. This time it posted, and got as far as "No keyboard,
or non system keyboard present" error.

Re inserted keyboard plug, then pressed restart button again. This time it
all booted up, apparently normally.

Two questions:

(1) WTF happened?

(2) Having force restarted it, should I run some sort of disk check
utility on my partitions? If so, what should I use?