Hello Alex, Thank you for your answer.
I set up the project by copying the source folder from my old computer to the new. On my old computer I have the 4.6 version of FB. On the new one I installed the 4.7 premium version from Adobe creative cloud. I thought that the version difference was the problem but the error has continued to pop up after replacing the 4.7 vresion by the 4.6. I will reinstall FB 4.7 and try to set up the project manually after having cloned the git repository. Again thank you :-) Vincent. -- Sent from: http://apache-flex-users.2333346.n4.nabble.com/
