one keyboard shortcut that may be of interest to you is Ctrl-Alt-Backspace. This shuts down the x window system and should return you to a command prompt or to a login screen depending on how your distro is configured. i am at work on a windows system and don't remember the full path, but you can turn off power saving hibernation through the control center in kde. i think that it is control center - power control - display power control. here you'll find controls for standby, suspend, and power off for your display. also something that could be of use is to open a terminal window and run the command:
this shows a list of running processes and what system resources they are using. when this is open, induce a system stall in whatever way you have before, then look at the top display and see what process is hogging/lagging the system.
hope this helps.