If any of you have changed you master cylinder recently I bet it's due to the rod adjustment or the pivot ball inside that trans bell housing. Many heavy single disc clutches are known for needing adjustment. I've ran into this problem on various hydraulic systems. Watch the videos on jacks transmission website to get a better understanding. The video has a trans for a DSM but it's the same idea.

http://www.youtube.com/watch?v=vYJxQyjIhUw&sns=em

http://www.youtube.com/watch?v=omAw-TgCYzM&sns=em