Flash Builder 4.7 Error: "dx tool failed"

The annoying bugs of Flash Builder 4.7 continue apart from my last post.

This time, the Flash Builder 4.7 throws me this error message: "dx tool failed" while I try to perform the Export Release Build, as shown in the picture below:

"Error occured while packagin the application: dx tool failed"

The thing is, every thing works properly in the debug mode. The error message only appears which you are packing the application.

The wild search from the search engine doesn't bring me too far. I haven't modified anything critical, except Remove and Add back the necessary SWC file before packaging. It definitely has nothing to do with the corruption of JRE.

Finally? I restart the computer. And the "dx tool failed" error disappears. Right. It is another workaround that doesn't bring any insight to the root of the error...

Can anyone tell me what has happened?