sorry about what I typed above, it was out of frustration. Well here's what happened to me I initially connected my Revo via HDMI to a samsung HDTV (full HD) during setup. Later on as I wanted to use it with another HDTV (this time NON full HD), the screen shows "Mode Not Supported". Apparently the genius Revo doesn't seem to detect and auto adjust itself when connected to a different TV. So I had to go back to my Full HD tv and reduce the Revo resolution on there to something supported by my non full HD TV, and well that seemed to fix the issue.
If this doesnt help, try changing to a different HDMI port on the TV. If that doesnt help, just chuck it in the bin and go to bed.