Shortly after starting up, a dark 'film' slowly comes down over the screen and I get a message saying I have to shut down the computer. I've tried to start from the disk, and before I can even run a repair off utilities, it happens again. What's up?

What you are seeing is a kernel panic, often but not always connected with a hardware or peripheral issue, so, unplug everything except mouse and keyboard, reboot and hold the shift key as soon as your hear the chime, continue holding it until you see the Apple Icon and spinning progress indicator, then post back.

It will take noticeably longer than normal to start.

I've been having this same problem for the last few days. I did exactly what you said. It says "safe boot" in red on the log in screen. When I log in, that "film" still works its way from the top of the screen to the bottom and I have to hold in the power button to turn it off. Now what do I do?

Did you do as I asked the OP, unplug everything? (except kbd / mouse unless this is a laptop)

Yes the only thing plugged in is the keyboard and mouse...

Startup in safe mode and test whether the problem resolves or not.

No luck. The film starts covering the screen before I can even finish logging in. Any other ideas?

A trip to the Apple Store, 😟

Yea I was afraid of that. Well thanks a lot for all your help...

You're welcome