Compiling producing inconsistent SWF and causes errors with embedded PNGs/GIFs

Question

I'm not sure if this question is better asked in this forum than here: http://forums.adobe.com/message/4685405
In short, whenever I compile and run my Flex project, sometimes the SWF throws the following error or similar:
Error:
ReferenceError: Error #1065: Variable ItemDetails__embed_mxml_assets_printer_gif_1274103970 is not defined.
          at ItemDetails()
          at mx.managers::PopUpManagerImpl/createPopUp()
          at mx.managers::PopUpManager$/createPopUp()
          at MyProject/btnPrintClick()
          at MyProject/__btnPrint
I thought is was related to the image but it's not and rather simply recompiling may cause it to work the next time. It seems sometimes images are left out and other times included. The error only shows for icons in my popup window and not the main app. I'm converted my Flex 3 app to Flex 4, so it uses the legacy MX tags. I compile to 4.5.1a. I'm using FB 4.6 on Mac OS.
The closest I've found to an explanation is this: http://kachurovskiy.com/2010/storing-icons-in-external-zip-and-seamless-work-with-composit e-icons/
Please advise.
Thanks,
code_away

Answer 1