Illegal override of activate in mx managers SystemManagerProxy – Solved

I’ve been quiet on the blog front for a while. ?I was having a rough time scuba diving in the tropics and so on…

Now back to business.

I’ve been working on migrating our core Flex 3 app to Flex 4. ?One of the problems I encountered was embedding an external swf file into the main app. I was getting the following error:

#1053 Illegal override of activate in mx.managers.SystemManagerProxy

It turned out that my Flex 4 app didn’t like the external swf because it was compiled with SDK 3.0. ?Sounds obvious, but it took me half a day to figure it out 🙂 ?I compiled my external swf with SDK 4.0 and everything worked beautifully.

So the lesson learnt is that if your app has other project dependencies, make sure they are all compiled with the same SDK version and you should be sweet.