Ok, I have been using the same BC recipe for years (1/2 butter, 1/2 shortening), but lately I have been getting air bubbles that form between the cake and the frosting. I always cool my cakes overnight, so they are not warm when I ice them. I just can't figure it out! The only thing I can think of is that it has been humid here lately, but I decorate in the AC soooo.....can anyone give me some clues as to what is going on?? It's driving me crazy cause it messes up my purty icing when I have to pop and fix bubbles! Thanks in advance!

These are sometimes referred to as cake farts or blowouts. If you see any threads about that check them out for suggestions.

I really don't think anyone has solved this problem completely.
Some people recommend you make a pin hole at the top and bottom of each layer all around the cake about 1-2" apart. They will be covered by the boarder but should allow for air/gases to escape.

I read somewhere that it happens if your cakes are cold or if they are not settled. Fill and assemble your cakes and let them set for several hours before icing them.