My car clutch began dragging a few weeks back. It turned out the bearing between the gearbox input shaft and the crank has siezed. Now I've replaced a number of clutches over the years and never had one of these fail before. The last two clutch changes (different cars) have been because of this bearing. Both had done over 100,000 miles so I'm not complaining, just surprised. Both times I replaced the clutch at the same time as they had worn low but neither had actually worn out and weren't slipping.
John