You need to manually update Punkbuster.
Google pbsetup.exe. Run it, a little window will open and it will appear to be updating then it will stop on a main Punkbuster window with more options, go to 'Choose Game', which of course will be Battlefield 2, once selected it will show up in the main window, highlight the game in the main window, then at the top of the punkbuster updater window choose 'Update'. Then it will update Punkbuster for Battlefield 2.
That will fix it.
