DivX AAC Encoder Memory Issues?

I'm loving the h.264 codec. Fast and nice quality video. But I'm running into a little annoyance with the AAC encoder. Perhaps I'm not doing this in the most appropriate way, but my method is this:

1) use DGIndex to demux, extracting all audio tracks as ac3
2) open up ac3 files in Audacity (using the FFMpeg filter)
3) output to file in raw format (48000/16)
4) encode raw audio file using divxaacenc (specifying sample rate, number of channels, bits per sample, high efficiency mode 1, and bitrate)

This method is the only way I could figure out how to get 5.1 audio using the DivX AAC encoder.

So it works alright...just a little problem with the fact that it consumes all the memory in my system (4gb total). Only seems to happen when encoding raw audio, and, in particular, implementing high efficiency mode.

Any info? Ideas? Suggestions?

Thanks