I think this has to do with the way Blitz3D is working with the windows-libraries. In windows 7 everything is different.
It turns out that Vista also behaves weird when you try to play Stranded II. That's why I believe this might also work for vista.
I have released an exe where I have removed multiplayer-related code, so if multiplayer wasn't working before, it sure is going to be totally dead now.
Just copy the exe in besides the original StrandedII.exe, and try to run. You can rename it too, if you'd like.
Version number should say "1.0.0.1SP", where the "SP" stays for Single Player.
Please tell me how it goes, test it if you have issues on windows 7 or vista! And have a backup of the original StrandedII.exe just in case. This fix comes with no guarantees.
The possible fixed exe:
http://www.prozhen.no/files/StrandedII_win7.exe
I also just started a blog at
http://www.prozhen.no about modifying the sourcecode, check it out if you'd like.