Hello,
i had a problem with the game stuck at 100% install, configuration utility not working and the game getting stuck on loading screen which was pointed out on some other threads here. First thing i checked was the antivirus so i disabled it but no luck, then i thought it was vista (but it used to work on my other machines with same OS, and even on this pc i remembered it working).
In the end i solved the problem by checking the error logs and noticing the AACW.exe was stuck waiting from something happening with the process aacenter.exe.
aacenter.exe is a file installed by asus mainboard acpi suite and stopping the process made american civil war running properly.
To make things even more odd, i had the same problem with napoleon's campaigns and birth of america, but after some attempts they started to run even when the aacenter.exe process wasn't stopped.
I hope these info can help you fixing the problem of your game interacting with this process cause i guess this issue could be quite common.