Yes, on some servers. If your game server is using TCP and sending less then 40 bytes on any packets, then FG will drop those packets. This will prevent you from sending and recieving such packets. This is due to FG dropping micro-packets (these buggers), which are commonly used for attacks. If your game uses UDP, then FG will not bother those packets.
The game I created uses roughly 12 bytes per packet for quite a bit of packets. I've more or less had to add in padding to my packets so FG wont drop them