Cannot Convert 6 Channel AAC to 2 Channel AAC - Help?

[Rez.]

Hello all.
I currently use my Xbox360 to stream HD media from my PC to my TV set. I've been happily converting my MKV collection which most of the time has either an AC3 or DTS track to MP4s with 2 Channel AAC audio (This is an Xbox360 limitation). I've been using MEGui to do this and so far it has worked a treat. My usual work flow is as follows:

- Extract Audio/Video/Subs from MKV with MKV Extract.
- Convert AC3 Audio with MeGui (Downconverting 6 Channels to Stereo in the proccess).
- Muxing the Video/Audio/Subs back into an MP4 (With MeGui)

The problem arises with a few MKVs I have that I used 6 Channel ACC on. I can extract the Audio just fine with MKVExtract. The conversion proccess from 6 Channel to Stereo is a problem. MeGui throws an error, It can't use Directshow to decode the audio. Xvid4PSP just chokes and causes VS2008's Debugger to kick in and then exits. Besweet Won't convert it either.
I've installed FFDshow and also installed Coreaac but neither helped. Graphedit tells me it can't render the file. I honestly don't know where to go from here. I thought it was a simple matter of not having the appropriate codec installed to decode aac, But that doesn't seem to be the case (Unless i've missed something). The files plays fine in Foobar2000 - So I'm pretty much fresh out of ideas.

Can any one shed some light as to what might be going on here? Any input would be appreciated, Even if it's just a nudge in the right direction. As alwats, Thank you from reading.

[poisondeathray]

Leave the audio in the .mkv container and use MeGUI. If you have more than 1 audio track, make a new mkv using mkvmerge (uncheckmark unwanted tracks). Make sure you have haali splitter installed, and ffdshow set to decode aac audio

[Rez.]

Thank poisondeathray, That did the job nicely.