Reinstalling with manual activation did not work either (even with registry cleanup).

However, I seem to have it fixed now... Don't ask how, because I really don't know exactly.

Sequence of events this evening:

- Uninstall + registry cleanup
- Install with manual activation
- Uninstall + registry cleanup
- Install normally, still not working
- Install Estonia Migration Tool
- Install FSX version of CS 777 1.4 on top of the P3D V2 install
- Start P3D in Legacy Mode, now all is working, with the FSX version though
- Uninstall both, leave registry as is
- Reinstall the P3D version of the 777 1.4
- Bam... working

Weird stuff going on. Thanks for all the suggestions, I'm just glad to have it fixed now.