"connection to host lost" when joining games with ~4+ people

[Golol]

logs:
https://www.dropbox.com/s/xj2cks40u0acy05/logs.zip
this is a bug i have had for a very long time but i was too lazy to make a tech support thread.
whenever i join a game that has more than 3 or 4 people this happens:
i do get in the lobby and in the chat box it says connecting to [host]. sometimes i can see the players in their slots, most of the time i can't.
the lobby is frozen like this for 5-20 seconds, and then i can chat and do all kind of stuff (others can't read what i chat). after a few seconds seconds i get a message "lost connection to host" and i have to leave.
then i usally repeat this process and sometimes i can join the lobby just fine with the second attempt but often it takes 3, 4 or more attempts, often resulting in me not getting a slot in the game.
this is just speculation but to me it seems like i can connect to the lobby without problems when my faf already "knows" the players.
what i mean by this is that it seems like when i try to connect to a lobby, lose connection, and then reconnect, while no new player has joined or left in the meantime, it works.
but if i fail to connect, try to reconnect but in the meantime players have joined or left i can't connect again and have to try it another time.
after a failed connection attempt i get the proxy server pop-up.
i tested if i can conenct to the proxy server and it told me i can.

[E8400-CV]

It might also be an hardware issue. I once had a modem (Linksys AG041), (now replaced by AG241 under warranty) that would crap out when it opened up a lot of connections. For example: the entire connection would crash when getting the server list for games such as Medal of Honor.