Originally Posted by Brad from the OC
Check your coolant level and do the venting procedure. If it doesn't recirculate the coolant and vent, then the water pump isn't working.
+1.I always hate to go to worst case scenarios, but water pumps are known to go on X5's pretty randomly. I've seen the average repair bill for a new pump install to be about $1200, If you're handy with wrenches at all you could do it for cheap , but its time consuming http://www.bimmerfest.com/forums/sho...d.php?t=598167
. Hope everything works out for you.