I was creating a build of one my AIR applications this morning and I get, "Error Creating AIR file: 103: ERROR, application.icon". I was like, what the h*** is that. I had an idea of where the problem may have occurred because I had just changed the .app.xml file, but upon first glance I really didn't see anything wrong.

Turns out, that when you get that error it is because of something being out of whack in your .app.xml file. I had un-commented a piece of code in there that should not have been and that was the cause of the error. So be careful editing your app config file.