Brakes? Ujoints?

I have a 95 chevy reg cab truck. Last night I was backing out of my driveway when the wheels suddenly locked up on me. I engaged my clutch, and put my foot on the brake and the truck was good to roll another 10 or so feet until locking up again. Does anyone have any clue what this could be. The truck has NEVER done this before. Thanks in advance for the help everyone.