I've had two of these warnings appear on the iDrive display while driving on an incline with my 2011 X3 28i within 17K miles.
Here's BMW's answer/fix:
Cause: AT001 Miscellaneous Automatic Transmission.
Repair/Parts: 17035 Software error in the vehicle, 11 03 12 defect code 11 41 09 29 00
Labor: Op 00 00 006 and 61 00 730 as per Bulletin, Updated complete vehicle software using ISTA 2.47.3. Clear faults and road test to verify repair.
