I have had this issue with the last 2 wedding cakes I deliver.  I ice the cakes and then stack them and then after they sit for a bit I notice they bulge where the cake layers met.  Upon delivery I notice it a lot more, even on the top layer.  Do any of you have this issue and how do I stop it from happening again?

Use the search box on the top right of the screen and search for 'how to settle a cake' or similar - I would imagine that you will be able to find heaps of useful information by searching that. Good Luck.

I've heard the argument many times for doing this or that to prevent bulging, but my own research revealed that its not the cake...as long as the layers are fairly level...it's the icing. 

"Wet" icings...icings that incorporate liquids, tend to very slowly flow and sag. 

Try an icing that has no added liquid (SMBC or one like mine that's only butter, shortening, powdered sugar and flavorings)  and see if that doesn't solve the problem. 

I've made hundreds of cake since I switched to this type icing and never had another bulge!

AAre you letting your cakes settle? Once filled, I let all my cakes settle over night.

Yes, I fill them and let them set.  I'll then ice them and let them set again before I stack them.  There seems to be a bit of settling after that, but not much.  It's just on the drive to deliver them that I get bulges.

The butter cream I use is powdered sugar, butter, margarine, vanilla and 3 Tablespoons.  So there's not a lot of liquid.  If I add to much, then it just slides off the cakes; this isn't the issue I'm having.

Are you putting a dam of icing around the layers, then filling in up to the top of that dam?

Most people tell you to use a coupler without a tip to make your dam but I've found that usually causes the bulging.  I always used a tip 12 and stiff icing and the filling only goes up to the top of the dam.  HTH