Why isn't music playback in sync between my computer and airport express after installing firmware version 7.8?

After installing Airport firmware version 7.8 update, music playback is no longer in sync between my computer and the speakers my airport express is connected to. I am using a brand new MacBook Pro with no special software and my speakers are connected to my airport express with a standard aux cable. I am playing music through iTunes.

Before I installed firmware version 7.8, I had no sync problems.