Hi, I'm a new member of the forums. I had the same problem and have just find a "solution" that worked for me. In my case the problem was not in Shogun, but in Starforce.

For those that don't know what Starforce is: it's a copy protection software that is included in some games (more each day it seems). In this thread in the Wargamer's forum you can find a guide to know if you have Starforce installed and a link to an uninstaller: http://www.wargamer.com/forums/tm.asp?m=100639

I used the utility mentioned in that thread to remove Starforce, and after restarting the computer, STW worked fine. So you can try this to see if it's your case too.