Aside from the DVD aspect. Can you plug the HDMI cable in and duplicate the desktop screen to the TV? Can you see the desktop if you cast?
I have an Insignia brand Roku TV that was notorious for acting strangely with a computer hooked to it's HDMI inputs. About 50% of the time I had to go unplug and remove the input, then plug it back in. Sometimes I would also have to restart the computer and do the process again. In spite of that part I never really had issue casting to it.