Mageia 1 (KDE) is locking up (other than mouse) fairly often

I have been running Mageia 1 for a couple of weeks or so on both desktop and laptop and am happy with its speed, looks etc. However, on my desktop I am havinga real problem where the system just stops responding other than the mouse still moving around the screen. Everything else dies. I've had a shell open with top running and can't see anything that particularly is hogging the resources.
This has happened twice today and both times I've had to hit the reset switch. A couple of times this has happened I've been able to do CTL -ALT-Backspace and recover relatively gracefully.
dosbox and Firefox while running Adobe Flash videos on you tube are the two apps that seem to be running when this happens.
Can anyone suggest a away of tracking down what is going wring here please?
Thanks.
This has happened twice today and both times I've had to hit the reset switch. A couple of times this has happened I've been able to do CTL -ALT-Backspace and recover relatively gracefully.
dosbox and Firefox while running Adobe Flash videos on you tube are the two apps that seem to be running when this happens.
Can anyone suggest a away of tracking down what is going wring here please?
Thanks.