What's up with this? I have played on some servers recently, but now I receive this error message after the map has been loaded. I then get kicked back to the menu and this error message shows up: Server disconnected - unpure client detected. Invalid .pk3 files referenced.
If it keeps coming back; uninstall, delete your et folder. Reinstall.
Unpure usually means you have extra skins, mods, or even hacks onboard, and Punkbusters too much of a Nazi to accept this for certain servers, thats why you must remove those in order to play on pure servers. =p