Weird freeze

[Joe Zeff]

It just happened again.  I have reason to think that Firefox is 
responsible, but at present, it's just a guess.  (One way I can tell 
it's happening is that I have an analog desktop clock running, and don't 
maximize windows.  As long as the sweep-second hand's moving, I know the 
box hasn't froze.)

None of the Magic SysReq keys worked, and I ended up using the reset 
button again.  After rebooting and logging in, I opened a terminal and 
as root ran

tail -f /var/log/messages

to watch what, if anything happened.  I then used RightAlt-SysReq-r and 
saw the response that the keyboard had been set back to default.  Using 
s caused an emergency sync, so I know that it works when I'm in X, 
something I hadn't tried before.  Now we know, it's not just X that 
hangs, it's everything.  Any suggestions as to how to find out what's 
causing this?  (If it's lack of RAM, I'm kinda stuck as the mobo's maxed 
out and I can't afford an upgrade ATM.)