My 2012 Altitude has the same problem, bought it a month ago, i have put it in for service three times to get it fixed, when i picked it up on monday of this week, they had ordered new clips. When i got to where they had parked it, it was already popped out again. They couldn't believe it. The service manager came out, and we went and looked at some other 2012 GC's on their lot and three other ones had the same problem.
This is definitely a engineering design / quality control problem! My wife's 2011 GCO doesn't have this problem.
The manager said he will file a tech line star report or something, it is bad when they have a bumper to bumper warranty and can't keep the front bumper on!
I am trying to enjoy my Altitude but this is disconcerting to me!