FLASH BUILDER 4.6 THRESHOLD
I had the same issue with Flash Builder 4.6 PC, the internet reveals that one should 'hack' the sdk CONFIG file found within the software installation location.
That did not work for me...MY SOLUTION:
What did work was the simple fact that I discovered that my project had 'mp3' files which apparently exceeded some sort of threshold of Flash Builder (mobile workbench). The mp3 files were files I rendered at high quality bit rates...my gut told me to try rendering them out to the standard 128 rate and that solved the issue.
This is of course a shame for Flash Builder and hinders my original approach towards developing mobile apps. I still have more testing to do on such a threshold but this is a very good thing to know.