Bit Torrent/.shnf file Magic Number?

I'm kinda new to the bittorrent thing. I downloaded Azureus last night and managed to get a WSP show in the menu as a .shnf file.
When I used to B&P/trade shows I'd mostly request that the show came in a .shn format. I then used the mkwACT software to convert the .shn to .wav files.
I tried to do this to the WSP show and also a Little Feat show, but I got an error when I used the decompression software with the .shnf files that said "no magic number". I had the MD5/sum check files there, but I still couldn't get it to work. Anyone know what this magic number thing is?

It indicates a corrupt file.