I had the same problem and got rid of messages by deleting all iOS 6.0 (including beta) data from ~/Library/Developer/Xcode/iOS
DeviceSupport.
Now, symbolicate uses the symbol data stored at /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport/6.0 (10A403)/
instead of the stored symbol data in user library.