Air Con Compressor Drive Belt

[grendawkin]

During a recent spell of fine weather I discovered the Air Con was not working on my X3.
I traced the problem to the Compressor Drive Belt which had fallen off and was lying on the sump protector.
The Belt looked in good condition so I refitted it and the Air Con works fine again.
After speaking to my BMW dealer it seems this is a common problem caused by a faulty crankshaft pulley. The dealer tells me that the Belt will keep falling off until the pulley is renewed (at large expense)
This on a Car which has covered only 30000 miles, expected better from BMW.