Had this problem with my 1995 apv. One day while traveling on the turnpike doig 75 and my wipers stopped during a downpour...I decided it was time to fix it. I went to autozone and bought a wiper motor. It's a little tight to work on, but after putting the motor in NO PROBLEMS. My neighbor used to be a GM technician and he told me this is an extremely common problem with GM vehicles.
The wiper motor comes with a lifetime warranty so if it does happen again...FREE.
It's been 2 years so far with the new motor and the wipers work beautifully.
Mike