German ISP 'WilhelmTel', dont think this will help you :) 100mbit downspeed
and no i had no problems playin dayz arma2 mod... also what might help is that the game worked before the latest update and I just checked again, if i connect via Friend it works, when i connect by pressing the Play-Button it also works.. only if i connect on the internet-tab it disconnects my internet...
btw sry for my english its not the best :)

well im having a similar problem... when i connect to a server i can join but once im on the server i get the red desynch symbol. after a few seconds it turns into no message received and i get a complete internet disconnect, my router then starts to reconnect...
if i join a friend however, i dont get this problem.. its just when i connect on my own to a server