The latest version of Xcode 4.3 has a serious bug that frustrated me quite a bit recently. If your project has Folder resources in it and these have sub folders with same names in the folder hierarchy, app compiles / builds fine but fails to submit with a completely unrelated error.
Finally had to download an old version 4.2, compile and submit using that.
Finally had to download an old version 4.2, compile and submit using that.