I had the same problem about 6-9 months ago with the clock plus also started getting low battery charge warnings. I expected this because my work commute is only 3 miles and have the under drive pulley... Plus the wife prefers we drive the rover when she is in the car with me lol. Before buying a new battery I bought a charger from Pepboys since its good to have one at home anyway and charged my battery overnight. The charger didn't return a dead battery warning ... some models also check your battery. I've not had the problem again and every other month or so when I Think about it or while cleaning the car I hook it up preventatively but still has gone months without charge and no problems.
2009 M3 : 6MT : Carbon : Silverstone : Fox Red Novilo : Aluminum Trim : Tech Package : iPod :
MODS: Performance Spoiler: Clear Reflectors : H&Rs : Escort 9500ix hardwired : Tint : Macht Schnell Filter : RPI Scoops : Rogue Pulley : Fabspeed resonated x-pipe with Remus Race : ESS Tune: TVinMotion