Why do my 99 Malibu's ABS Light and Brake Light come on sometimes after starting the engine?

Sometimes when I start my 99 Malibu (V6), the Brake Light and ABS Light will come on and stay on for a few minutes. This is usually accompanied by the power windows and vent blower not working until I rev the engine a little. The car seems to be running fine once I start driving. I've checked the brake fluid... show more Sometimes when I start my 99 Malibu (V6), the Brake Light and ABS Light will come on and stay on for a few minutes. This is usually accompanied by the power windows and vent blower not working until I rev the engine a little. The car seems to be running fine once I start driving. I've checked the brake fluid and it seems fine.

I was wondering if this is some electrical problem. I had the battery tested, it was okay, but the terminals were corroded. Right after they were cleaned, I tested my car to see if this fixed the problem. The Brake and ABS lights came on the vent wasn't working until I heard a click from the engine, then the fan was on and the lights off. Other instances, the two lights will come on when I first press my brake pedal after start-up. Could some of this be due to a relay problem, bad battery connection, or something else?
Update: The brake fluid is okay, the parking brake is not engaged, and there are no blown light-bulbs, braking or otherwise. How could I tell if it is a grounding issue? Is it hard (or expensive) to find and fix?
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