I had this issue with my 07 335i, it was covered under warranty. They reinforced the headlights. Not sure how, but the problem was taken care of thereafter.
Current:2011 BSM E92 335i
Sold: 2006 Midnight Blue Cayman S
Sold: 2012 Lightning Red WRX
Sold: 2007 Monaco Blue E92 335i
Sold: 2006 Aspen White STi