I am having the same problem as the OP - disconnects 5-30 minutes into the game, very frequently.
Open ports 6112-6200 - done. Even gave them the highest QOS.
No firewall blocking - done. Windows firewall set to allow demigod.
/serverproxyonly - yes, done. Still DC's frequently with that parameter on.
No firewall or packet blocker on my own machine - done
Additional Info: I'm using Windows 7 - I believe Frogboy himself encouraged me to do this, so I'd be a sad panda if this was the problem.
ISP: Teksavvy Internet Solutions, a Canadian reseller of Bell DSL.
Router: WTRG54L with Tomato Firmware
It's a bit of a mess because we had to recreate lobbies a few times - but the relevant info is right at the end.
I am having the same problem as the OP - I can get into a lobby with low pings and connections to everyone, and play the game from anywhere between 5 and 30 minutes.
I can sometimes complete short games. But I very, very frequently get a disconnect between 5 and 30 minutes into a games - the typical scenario where it looks like everyone has left
the game but me.
Alright, I followed the instructions to the letter.