The parking brake mechanism consists of a lot of little springs and connecting pieces that will rust and fail. I had my parking brake seize up because it wouldn't disengage and almost started a vehicle fire -- when I pulled over it was smoking like hell and stunk like burning brake shoes. I ended up cutting the cable and drove without a parking brake for a couple years before I finally ponied up, got all the parts from eBay and had the local (only) honest mechanic replace everything for a couple hundred bucks. You should get someone to put it on the lift and make sure its disengaging and if it isn't, cut the cable and just leave it in gear when parked till you can get it fixed. My $0.02...