Problem with FD gearbox - jammed in 5th gear?

[Welsh Dan]

As above.

Driving home on friday, put it into 5th, went to change back to 4th a few miles later and lo and behold, I couldn\'t move it from 5th.

I\'m unable to move the gearstick into the neutral position, however, we have pushed the car a bit and its not in gear, although there is a bit of a grinding noise which suggests its only just out of gear. Its a 4 month old clutch, so its not that. The gearbox is going in to be looked at on wednesday, but are there any common problems with it?