A new debug version of Flash Player 9, 22.214.171.124 to be exact, is available at this link:
As of today, the Flex Builder 2 download contains this new debug Player.
We released version 9.0.16 as a Release (non-debug) version and 126.96.36.199 as the debug version. If you had already installed 9.0.16 you were not able to ‘update’ it to the debug version, 9.0.15, because of the rev number.
The updated Flash Player 9, debug version, 9.0.16, fixes that problem.