I just got disconnected from a server due to having an out of date version of punkbuster so everyone else will probably have the same problem. Before you play make sure you update punkbuster.
Download this: http://www.evenbalance.com/downloads/pbweb.exe and copy it to C:\Program Files\EA GAMES\Battlefield 2\pb (or wherever you installed bf2). Run it and leave it for a while so it can download all the updates and only exit when it tells you to.
Update Punkbuster before playing
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