http://www.punkbuster.com/publications/aa-...ex.htm#enabling
QUOTE
There are two ways to enable / disable PunkBuster software. You can either join the server logged in as a server administrator and use the following console commands (without the quotes): "admin pb_sv_enable" or "admin pb_sv_disable". Alternatively, edit the pbsvgame.cfg file in the "System/pb" folder and use "sv_punkbuster 1" or "sv_punkbuster 0" respectively. If pbsvgame.cfg is edited or changed, the server instance must be restarted for the change to take effect.
NOTICE: PunkBuster cannot be Disabled immediately during the middle of gameplay. Choosing to Disable PunkBuster by any method will set PunkBuster into Disabled mode but that does not take effect until the entire game is restarted. Neither Players nor Server Admins can simply turn PunkBuster off and on during the middle of gameplay. Once PunkBuster Client and/or Server has been Enabled for a gaming session, it becomes Enabled immediately and then stays Enabled regardless of how many times the Enabled/Disabled mode is toggled. When the game is exited, the current PunkBuster status is saved and the next time the game is started, PunkBuster will initialize to the mode in which it was last set, either Enabled or Disabled.