Character encoding fed into flash players is bad.
Resulting in filnames with å/ä/ö dont work.

Could you perhaps provide more information (http://www.zenphoto.org/support/topic.php?id=3760)? I have a video named Tëst Videø which is working just fine.

(while im asking)

How do I implement player support in a theme?

02 - Division Of Laura Lee - We´ve Been Planning This For Years - Black City

There is no need to implement player support into a theme. Just activate one of the two flash player plugins and that's it.

I had to rip the picture displaying part from an official theme to get it working.

Ok, it would have been helpful if in the first place you had posted what theme, zenphoto version, etc. you were using.

We of course cannot be responsible for things not our doing.