ok...
the paintball2 program wont automatically download the update you need to continue playing. SO, you go to that link above and download the update for paintball2 and install it that way. thus solving your problem.
EDIT
oh excrement. Didnt read properly. MY BAD.... again :S
erm... check firewalls, etc. Make sure you can play on the maps you already have.
or go to the otb ftp site and download all the maps.