You have to hate it when you have your mates all lined up to play a multi-player online game and you are the one with the sick computer.
They are very kind about it but you know they are muting their microphones and shouting “muppet” at you. Or worse.
For me it was trying to get Dawn of War II to connect to Games for Windows. It just kept barfing. Arrgh.
Tried unlocking the necessary network ports: UDP 88, 3074, TCP 3074. Nope. Didn’t do it.
Tried opening the access-list on my trusty Cisco 1702. Nope.
Then we looked at the MTU on the PC. Aha!!
If you have your PC MTU set to a value lower than 1362, it fails.
Pop along to the MTU registry key (HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\), change it to at least 1370 (I recommend 1492 personally) and restart.
If you have specific values per interface, look at the keys for each adapter in turn: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\[Adapter ID] and create a new DWORD under each one called MTU with the appropriate value.
Good pair of links to read: http://forums.gamesforwindows.com/t/785.aspx and http://www.microsoft.com/games/en-GB/Support/Pages/troubleshootingIssues.aspx
Sorry guys!
