Neil
Speaking to my mate who owns a stolly, he says that it could be the clutch plates that have stuck together if it has been keft long enough without the pedal being depressed and clipped back, this takes the pressure of the plates if left longer than 3 days or so.
If the plates are stuck together then you must drive into a tree or wall to get them unstuck, or better still use a hammer, this is assuming you have the old style plates.
Does this make sense ??