Problems With My Garmin Sat Nav

[macpark]

My Nuvi Sat Nav has suddenly stopped issuing audible instructions whilst attached to the docking station. The device is not muted and is working perfectly in every other respect. When you take it off the bracket, the sound instantly returns. Has anyone ever experienced this? Is it possible to buy a new docking bracket if necessary?

[CrapAtCryptics]

Could you just define what you mean by docking station is that something other than the plastic ball and socket screen attachment.