I fixed this the following way (this is basically resetting the Power Management Unit — PMU):

I disconnected the computer from the power cord, and from all other cables.

I held down the power button for several seconds to turn off the computer.

I let it sit 5 minutes.

I restarted the laptop while holding down the Shift key.  This restarted the computer in Safe Mode, with the screen visible again.

After I logged in (in Safe Mode) to make sure everything was ok, I simply restarted the computer the normal way, and the screen behaved normally again.

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If that doesn’t work for you, you could try these steps, documented at apple.com:

Holding down Command, Option, P, and R to reset your PRAM and NVRAM

Resetting PowerBook and iBook Power Management Unit (PMU)

• Three operating systems:  Mac OS X, Unix, and, with not much work, Windows.
• A great TV, for watching movies ( and if you really wanted to watch cable, you could buy an adapter for that) .
• A great stereo, for your iTunes collection.

It’s  a little expensive, but I say it’s worth it.  The screen is really really good.  A friend of mine has an HP all-in-one flat screen, and he says his screen is not as crisp and bright as the iMac’s.  The design of the iMac really does complement any room.  Unlike any computer I can think of, it is not something you want to hide under your desk.  You’re perfectly happy having it out in the open.  It improves a room.

As for the software available for Macs, well, I’ve had it almost a year, and I haven’t had to buy anything yet.  I’m an average user for photos, music, and videos, and the free stuff it comes with is just fine for me.  For word processing I just use google online apps, and for developing I use free open source software.

Anyways, if you’re looking for a new desktop, get an iMac.