So, when playing the AIX mod for Battlefield 2, I kept getting kicked after about 2-3 minutes of play when punkbuster(!) complained that:

PnkBsrtrB.exe handshaking failed ; PnkBsrtrB.exe heartbeats stopped ; PB init failure ; Packet loss

The basic problem boiled down to the fact that when Punkbuster installed, it created the outgoing rules in windows firewall, but it did not create the INCOMING rules.  I simply added incoming rules for:

c:windowssysWOW32PnkBsrtrA.exe
c:windowssysWOW32PnkBsrtrB.exe

And set them to ‘allow’.  That turns out to fix the problem.

I still can’t believe how horrible the solutions to prevent cheating were back in the day.