Cannot join CoD4 modded servers

[F |Madness| U]

Basically, on my old PC I was able to join all servers with no issues. However on my new laptop, (with a legit CD key and copy of game may I add, same one as on my old PC but that PC isn't in use) I am unable to join any modded servers. Whenever I try to join a modded server it gets stuck on Awaiting Connection.. and says Awaiting key code authorisation. Note that I can join unmodded servers fine, also if I try to join a cracked modded server, it passes the Awaiting connection and gets stuck on Awaiting challenge.

I cannot currently try a full reinstall because I don't have my disc copy of the game with me at Uni, so any help would be greatly appreciated, thanks!

[x0ozero0x]

I haven't had this exact problem but the only advice I can give is to try removing your config_mp.cfg file from your profile and then try joining a modded server and let it recreate it our go into multiplayer options and renter/verify the CD key. I sometimes get an error just trying to look at the server lists deleting my config_mp seems to fix it.

[F |Madness| U]

Thanks for replying, I tried it but unfortunately it didn't help. I'm pretty sure it's something to do with the university internet in that it blocks some P2P ports and such, however it's just weird that I can connect to normal servers but not modded ones.