Stuck in 5th gear??

[Dodgentwo]

Ok a buddy of mine has a 99 5-speed. Was driving today and went to downshift from 5th. The shifter moved to neutral, but the truck stayed in 5th gear. The shifter like slipped out of the fork. This had happened once before and he thought it was the shift tower so he purchased a new one from quad 4x4. Now it did it again. So has anyone else had this problem? Or does someone know whats going on? And whats the cure?

Travis