Okay, I'm guessing by now you've either pulled the battery to turn it off or it's completely shut down on it's own. In either case, when you try to turn the system back on, does it seem to stop mid boot with both LCDs apparently on but black and the power indicator blue with no other lights?
If you've answered yes, then it's probably a fault in the lower LCD. I've fixed three older XL models by replacing the lower LCD screen and can confirm they work and are fixed that way. So with that, I would invest the $10-20 on a new lower LCD off eBay to fix your problem. Make sure you also have a #00-000 phillips screw driver or get a LCD that comes with tools so you can open it up and replace the screen.
I hope this helps get you back on track to playing, good luck!
Also follow this guide to replace your lower LCD: [guide|41361]. You won't need to remove everything they suggest here.