No audio with 5.1 AAC

After installing atV Flash 4.1, no audio plays when the audio source is AAC 5.1. For example, when the opening Apple TV animation plays, it is silent. XBMC will also play no audio in AAC 5.1 files. Turning the Dolby Digital Out to On in the Apple TV’s Audio & Video menu will enable audio, but only in stereo. XBMC can’t play AAC 5.1 (to my knowledge) but it will usually output stereo, at least it did before the update. Any help would be appreciated. Thanks.

Audio from Apple TV is delivered to a surround receiver via optical cable. DTS and AC3 files play fine.