Some tips to start with:
1) Download patch 1.4 for Silent Hunter 4.
http://www.ubi.com/US/Downloads/Info.aspx?dlId=2172 << This link may work for you to get the patches.
2) Make sure when you installed the game, you did NOT install it into the Program Files (or Program Files x86) folder, where it wants to go by default. When the game asks you where to install change it to C:\SH4 or similar.
3) After you get it installed and patched, try a test-run with no mods at all.
4) There is two movies on startup: the Ubisoft logo, and then the game movie. Do both of the movies play, or just one? This can indicate if its a codec issue or not.
I and others do run SH4 with Vista x64 with no problems, so hopefully you get yours sorted out
