My X5 too has developed this clunking sound for about 2 weeks now when I hit bumps even at a slow speed. Seems to be louder on the front passenger side. Thought it could be a problem with the air suspension (no faults though and I can still raise and lower the height) and my indy states that since my X5 has under 50,000 miles, he doesn't think it's the air suspension. Just dropped it off this morning and I hope all is resolved. ::::crosses fingers::::