Not enough info to diagnose. What hardware do you have? Wireless or LAN? What kind? What version of PCBSD? Security settings? Have you tried the PCBSD forum? They have a "Knowledge Base" with a lot of that kind of stuff for newbies. Go to the command line and type "dmesg" and <enter> and you should be able to figure out what kind of hardware your system has on it. You can get more info about your LAN or wireless card by entering "ifconfig". That may get you started.

Tony