that happened to me. the day after I brought the x5 home from the dealer with 82,000 miles on it. It's the CCV. water (condensation) gets in there freezes and the devil knows what is next. The dealer fixed mine for free.

You can fix it yourself for cheap or the dealer will charge about $500 or more to replace. there is a diy up top here. You need to make sure you have the heater to keep from freezing. Cold weather version.