Windows 7 RTM shutdown anomaly

As when booting in Safe mode the shutdown is successful and complete, this indicates that some third-party application is responsible for the problem.

To locate the problematic application, you may use the free tool Autoruns for Windows.

This utility shows all programs configured to run during system bootup or login, and when starting various built-in Windows applications such as Internet Explorer, Explorer and media players. You may turn off startup items with a click and return them later with another click. You may avoid listing Microsoft products by using the menu Options > Hide Microsoft Entries, Hide Empty Locations and Hide Windows Entries

I would suggest turning off startup entries in bunches, drilling down to the startup program that causes this behavior. Once identified, it might have some setting that can avoid the problem, or can be left out of startup and only be invoked when required (verify that once invoked it does not add another startup entry, but such can be deleted by Autoruns).