HitFilm Express Errpr 37 - I can't export anything!

No matter what render preset I'm using, I always get the error "Could not encode samples for frame 2"

The only render preset, that works is the avi preset, but the sizes of the files are huge after the export.

And if I try to render just a white plane or something very simple, it gives me always the same error. The only thing, that it can render, is just a black screen with no audio.

I hope that somebody can help me!