A new EA help page notes that the company is looking into a string of false Punkbuster bans that have hit a number of Battlefield 3 players.
We are investigating an issue of Punkbuster bans that were incorrectly applied to some of our players. Please undertstand that our game advisors are not able to access or overturn Punkbuster bans, but we're working with our partners at Even Balance to get this resolved as quickly as possible.

If you have been impacted by this issue, you can appeal the ban directly by following the instructions found here.

If this sounds like an issue you've run into, be sure to follow the above link to see what you can do to help your wrongful ban.