I actually could care less about smoothwall, goto www.snort.org
My bloody evilness.. did you see what his errors are?

Initializing Network Interface eth0
ERROR: OpenPcap() FSM compilation failed:
PCAP command: %s

Fatal Error, Quitting...

Which is a snort error when a NIC cannot drop into promiscuous mode.
It makes a bloody big difference to the problem..
There are differences between Snort for Linux and Snort for Win.. for a start the Win version is a Port from the *nix..
Smoothwall V2 is an operating system based on Linux kernal 2.4.. It is not a windows application.. Giving a windows solution to a application running under linux is like solving a submarine problem with Automobile solutions.. you may accedently hit the solution.. but you may sink in the process..

Also as already stated.. The Version of Smoothwall is important.. as there were problems with Snort under the earlier Smoothwall V2 beta's.. and in some the patches didn't solve all the problems with all hardware combinations..
Just using a different chipset NIC may be the answer, or try V2 b7 of smoothwall..

And yes i am in a bad mood.. and like Badfalls_girl.. I do bite..

cheers