Like Epoch, when my clutch finally went [at 96K], it was as a result of warped pressure plate fingers that refused to let the friction disk pull away squarely from the flywheel surface- a section of clutch disk continued to make contact.

This symptom was indicated by a very faint clacking noise when declutching- that increased and decreased with revs- shortly before the shifting between all gears became very difficult.

The fact that this only happening shifting in and out of fifth seems kinda weird. I'd check fluid level too. If the master cylinder seals were failing, I think you'd have this problem with all shifts IMO.

Anyway, my two cents.