In the previous article found here we reverted to 9.0.28 flash player because we still need the debugging version of flash player for Flex Builder 2. The approach is working and the debug is working again but sometimes in bigger application where a lot of actionscripting is involved some runtime errors are arising. It seems that the player found in “Player Backup/debug” is not the same with the last player (and in deed it seems to be the player from Flex Builder 2.0.0 not the one from the 2.0.1 update) and because of that some errors will appear. To solve this issue i found Archived Flash players available for testing purposes where different versions of flash player can be downloaded for testing purposes. I’ve downloaded “Flash Player 9 (debugger versions) (61.0 MB)” and from there installed the 9.0.28 version also as simple debug version and also as ActiveX. From now on the runtime error didn’t appeared anymore.