Citroen AX Driveshaft

Hi

My girlfriend has told me a mechanic has diagnosed a problem with her driveshaft on her Citroen AX N reg. He hasn't looked at the car, just told her about it from her description of it making noise. He said it's a common thing with these cars, but the girlfriend can't remember the technical details exept for he described cogs grinding together!??? Does anyone know what this common driveshaft problem might be on this car and ... most importantly... whether the problem is likely to lead to anything catostrophic!?? She does say it isn't getting any worse.

Thanks to any replies and thanks to those helpers with the Stag!

Jon