System keeps locking, how do I find out what happens?

[Mark Lawrence]

Hi folks,

By locked I mean that I can't get a response from the mouse and that the 
time on the top bar, which I have set to include seconds, stops 
incrementing.

I've found from a search REISUB and on hitting the R the system has been 
released, although more often than not I have to complete the sequence. 
  However on the last occurrence I tried not even the keyboard worked so 
it was power off and start again.

So which logs should I be looking in to ascertain what is going on as 
this is obviously extremely irritating?  Please spell it out in idiot 
terms as I'm not a linux expert, thanks :-)

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence