Open her up, find the row of three white potentiometers, and adjust the middle one in 1/8 counter-clockwise rotation increments until it works. A single 1/8 adjustment might do the trick; if it doesn't work after four 1/8 turns (aka half a full rotation), it's probably not going to work, and even if it does, you'll probably burn the laser out pretty quickly. You can hear it give off a weird high-pitched squeal after a certain point.
You don't have to dig far, by the way. Once you get the outer case off, you'll see what I'm talking about. Good luck!
EDIT: Given the number of times I've seen this fix be effective, I really think it would be a good thing to sticky. If a mod (Necromancer?) will give me permission, I'll make a custom thread.