bugzee

hi i bought arma2:OA a couple of days ago and have been playing single player quite happily, i then decided to have a look at multiplayer but i can join no servers and all i get is "bad version, server rejected connection". i have a few ideas as to why this may be: 1) i have not got the required mods for the servers ive tried to join (around 40 different ones so far) 2) all the servers are private and need a password? 3) i did have some problems with the cd key not being recognised, i didnt think much of it at the time and did not send an email to the support site as i thought i had got it working (if i can play single player would this be stopping me?) 4) my firewall is causeing problems? before anyone asks my copy is a legal dvd boxed version and i have patch 1.57. sorry if something similar has come up i did try and have a look but nothing seemed to help. please try and help me. thanks in advance.

thankyou everyone for all your input and help, i think i have got the problem sorted, will report back for more help if it's not fixed. thanks again

thanks Rindier i shall give that a try but does that mean that no servers run just arma2:OA 1.57, they all need mods?