yeah, i had this problem once when i gave my 185 an almighty thrashing changing from first to second....its like the clutch stayed half engaged, but when i pumped it again it worked fine and has done so ever since.
There is no damage to any of my clutch components i.e. pedal, firewall or lines. My opinion was because i had a HD clutch installed with pressure plate something may have gotten stuck? or something inside the gearbox itself, but i gave up investigating as it kinda stopped by itself...
Have you recently installed a new clutch, or is it an old one?