Is your Magnavox tv the LCD kind? i had this kind of issue and it was the monitor resolution setting, the manual said to "... NEVER use the hdmi port for a computer monitor application or it could damage the monitor..."
This didnt make sense so after looking further at it all I could conclude was that the PC screen resolution setting must be the same as the setting for the LCD monitor that you setup thru the remote control, usually this is about 1260x768 ? set the PC to that which means its not the greatest resolution but thats all you get, and then try the hdmi.
the warning seems to be that if you try to overclock or force a higher resolution onto an LCD television the LCD tries to run at that rate and could damage the circuitry? or screen? usually with computer monitors they have circuitry to balance the resolution and not do damage if its too fast or outside the range, so setting the monitor to higher than it can handle makes a blank screen.
I have an older 15" monitor sitting around to connect up to (the) PC to set the resolution before connecting it to a large LCD tv. hth