They will load for a while and then show the message "There was a problem playing this item."
720p works fine.
My computer should be able to handle transcoding, so I don't know what is the problem here.
What should I do ?
Edit: I tested the same file with Universal Media Server and it worked fine. So I guess the problem is with my plex server.
Edit2: I realized that plex showed me that there was a subtitle in the file I was trying to watch, but there wasn't any. So when I marked the option to not load any subtitles, it played the file without any problems. So problem fixed.