Talon have you posted a copy of your DxDiagnostic, or sent one to Skuzzy? Sounds like a sound card issue. Could be the map is loading down your VP and CPU and the sound card is losing out, you could have IRQ sharing issues that dont show up until one of the components is under a load............and could be a hundred other things too. If the sound card and mic pass testing offline, and its only when you are flying online you experience the problem then at least it narrows things down for you.
SA2