This has been bugging me for about 18 months.
Both abs and brake idiot lights would go on above 40 mph and stay on. I replaced the abs sensor on the pumpkin, traced and wrung out every wire and plug from the dif to the abs brain, flushed the system, reflashed the pcm and sacrificed a chiken on the hood...nothing worked.
I took it into a dealer to have the control module flashed after a tranny rebuild and one of the techs told me it was the brake switch on the pedal. I told him that it tested fine on a Fluke meter. He said that they build up enough corrosion on the contact to degrade the quality enough to trip the safety and light the lights.
I ordered a $16 after shipping switch because why not, It's easier then ramping up the sacrifices.
While I was waiting for it to arrive I removed the old switch, opened it up and took a piece of emery cloth to the contacts then blasted them with contact cleaner/conditioner (radio shack special). Now I have a new switch AND a perfectly good old switch with no lights on the dash!!

But maybe the voodoo chicken thing is what fixed it

 

I will be remembering this one! Good job.

 

X2, as I have this also. just started tho.

 

Good idea to clean all the contacts (there are three in the switch) but the culprit is the NO contact. The contact is closed when the pedal is up and opens when the brake pedal is pushed. The comp thinks your riding the brakes if there isn't good flow through the switch.