When I play halo wars online about 10 minutes in, it'll say everyone left the...

[jon]

...game and it will quit? It will say everyone else resigned then I win, but it's actually me that left. It can't be my internet because it's always connected! help?

 

[BL00DLUST_Reaver]

type in your IP address into your web browser, it will be on the bottom of your modem. look on privacy (or security) settings.

make sure your NAT is set to open.
i had the exact same problem, and this was the problem.

hope this helps