TIM--
Like others have mentioned, see if it's on both sides or just one side.
I had the same thing happening after my truck was repaired from being side-impacted in 1994. The rear axle seal on one side was leaking from where the left axle was replaced. The drum was being lubed, causing the other side to lock up due to imbalanced braking force.
Leaking brake fluid could have the same effect.
Good luck!
