The screen on my 540c seems to be totally haywire. Whenever I'm using it, the whole screen will go glitchy, jumpy, jittery, and then black. Then it'll come back, start glitching, jumping, jittering, flicking, and then go black again. What's wrong with my little PowerBook, my favourite of all my old Macs? It's unusable right now because of the screen. Just a few minutes ago it stayed mildly visible long enough for me to tell it to shut down

Please help! I love this little PowerBook and really want to help it!