I just had a bride e-mail me and tell me that the cake fell apart after I had set it up. She said that the corners fell off. I'm not sure how this would happen.
Any ideas?

I delivered the cake and set it up myself. At that point it was fine. I then put the flowers on (which were a bit heavy) and left.
If anyone has any ideas why this may have happened I'd love to have your advice!

I am assuming it was square since you say the corners fell off? Or was it round and the top corners?

Can you give us more info about the cake?
what type of cake?
was there filling?
what was it iced with?
How about the location?... was it in an air conditioned room? was it set up in a high traffic area or near the DJ? Was it inside or outside?
How long was it set up before it fell apart?

There are a lot of things that could cause it, without seeing a picture or knowing more info it's hard to help you figure out what happened.

Tell her you need to see pix before you can comment on what happened any why. And of course get answers on the questions from the pp.

Also what kind of support system did you use? If you stacked it you had to have them on some kind of cake board, which makes it hard for a corner to fall off, unless it was tapered at the bottom and the top corners fell.