Here are a few things to try
- Reset the unit by unplugging it and restarting it, see if it helps
- Pressing the setup button when the Mag254 is loading might get you into the setup, from there you can change the resolution to something lower
- Try another out put (not HDMI) and see if that helps
- You could also connect it to another newer TV if you have access to one and then switch the resolution down