Problem w/Multiplayer Voice FSX

The multiplayer in FSX is definately a step up. Granted it's not what we'd like, but it's candy is very sweet. My brother and I like to fly MP sessions alot, and the shared aircraft is very nice. The one thing we are having problems with is Voice. I don't know if we're doing something wrong here. Here's the deal.I have a Planetronics Headset, so I should be able to get simulator sounds through main speakers and voice in the headset. It works in the computer ok, but not in FSX. Well, it does for a few minutes then cuts out. I had it reversed, sim sounds in headset & voice in speakers, which is when it worked the longest. My brother is just using a mic, all sounds in speakers. Now we are on LAN, have tried general LAN connection and a direct connect with the same results. I'm not sure if voice compression is doing it, or because we are on the same IP. I mean computer has different IPs, so is that what we are supposed to use, or the modems IP. And I don't get why it works for like 2 mins, then cuts out.Maybe I'll have to try MP with someone outside my network and see if that works. Any suggestions out there?