My friend, a flight instructor, is teaching me how to fly a Cessna 172. When we are in multiplayer mode, he can host me, but I cannot host him. He is running MFSX Deluxe and so am I. His OS is Windows XP and mine is Windows 7. I have checked my security settings and have allowed GameSpy and MFSX past my firewall and we both have the same part setting range. When he shares his aircraft with me, it flys erratic sometimes. Can anyone out there give me some good ideas to fix this problem. I believe my plane would work fine in multiplayer, if I am hosting. Thanks, guys.