Hello Jonathan,
My first guess would be that some audio or MIDI driver that's present one the system (an ASIO, DirectSound, or MIDI driver) is hanging for some reason when Hauptwerk queries the list of available drivers upon launch.
Assuming you're using the primary configuration (as opposed to one of the 'Hauptwerk (alt config N)' desktop shortcuts), and assuming default installation locations, If you open the following file:
[your-Windows-account's-home-directory]\Hauptwerk\HauptwerkUserData\Config0-Logs\HauptwerkLog.html
... and scroll to the end, what do the last few lines show (e.g. copy/paste them)?
Also, if you reboot, then try instead launching 'Hauptwerk (alt config 1)', does it start properly?
If not, if you shut the PC down, then temporarily disconnect all audio and MIDI interface hardware (e.g. your Behringer interface's USB lead) from the computer physically, then boot the PC (with the audio/MIDI devices disconnected), is 'Hauptwerk (alt config 1)' then able start properly?