Clutch isn't in backwards?
Just had a buddie do that when he rebuilt his kick, he was all happy to just be getting it done. So while he was rushing to finish he didn't put the clutch in the right way. And it wouldn't shift with the rig running, but it did shift while it was off.
I hope you dint have this problem, cuz that sucks pulling the tranny again!!
Good luck
Amilla