I'm a complete Raspberry and Rasplex newbie - so please bear with me.
I just installed version 0.3.1 and booted the RPi. Everything worked fine but I noticed that the UI and movie player runs at 720p. I tried it against two TVs with the same results. The preferences do not allow me to change the resolution.
I have a similar problem. My pi is not directly connected to the tv, but through an a/v receiver. When rasplex boots without the a/v receiever being on, it comes up with 720p (which cannot be changed in the preferences). If the a/v receiver is already on when I start the pi, everything is fine - it comes up with 1920p (and this can be changed in the preferences).
Is there any way to force the rasplex to start with 1920p even if it is not attached to the tv when it boots?