Same problem here, /jp/'s solution didn't work for me.
Actually, I also had the exact same issue with both the
AoCF demo and
ULiL as well, and both cases required the use of some sort of modified .exe released by brliron for it to work in my case.
Does this have to do with DRM or having certain types of computers/components (GeForce vs Radeon, etc.)?
EDIT: I got a workaround. Download
thcrap and patch TH15.5 to your language of choice (even Japanese). Using the shortcuts generated by thcrap will allow you to bypass whatever that's preventing the fucking th155.exe from booting up and starting the game.