after trying to get g0ug's bf2 running (win7 64bit: he was kicked by pb after a few secs) we managed the thing as listed above:
a) look for all pb folders (program files, ea games, bf) AND appdata(hidden folder in USER) and delete them.
b) reinstall pb (see punkbuster.com for details)
c) search for PnkBstrA and PnkBstrB, they should be in windows/wow64 (not sure about the folder name) and memorize the path.
d) open system settings and klick windows firewall
e) there you have to set up a new OUTGOING rule for a file, so here you must enter the memorized path, then klick ok. this last step has to be done twice, once for PnkBstrA and once for PnkBstrB.
then start bf2 and the problen should be fixed.