Audio Volume Issues - MeetMe + G.729

Has anyone ever heard of issues with MeetMe and the g.729 codec? I am having sporadic complaints that one leg of a call has very low volume, to the point the user cannot continue and simply hangs up.

I have opened a ticket with my carrier, but I am just wondering if there is anything out there I should be aware of.

My basic configuration:
Dell 1950
Dual Core Xeon 3.33Ghz
100 G.729 licenses
Approximately 80 encoders/decoders in use
Approximately 50 conferences (each with 2 people)
Pure SIP environment