Apparently it is a very common problem with carbon frames with this type of integrated lugs.
I've had this happen to two Jamis frames this season alone, and I would say it is a general weakness for carbon frames.
It seems the problem is a lot of filler/epoxy is used in the lugs, because constructing a lug with the correct carbon layup is perhaps the most tricky part of the carbon bike construction. At least so I've been told! :-)
If you could take a look at the lug unpainted, you would see that whatever carbon weave you may see elsewhere on the bike, comes to a stop at the lugs, perhaps indicating a higher density of filler/glue/epoxy in this area.