After about 1 minute of operation I lose the picture when I change from HDMI 2 to HDMI 1 and then back the picture comes back for 1 minute then it is lost again. I moved the input to HDMI 1 and the same thing happens. I can pull up the menu fine wso I do not think the problem is with the inputs not locking in properly.

SOURCE: magnavox 42MF531D black screen

Common issue I have come across when using any TV as a PC monitor. Best workaround i found is just dont change inputs or reboot the PC and the tv will pick it back up.

SOURCE: HDMI Input only reads Digital TV and not PS3 or AV Receiver

Well, I won't take the credit of others. Many people have the same problem as you do.
In the search box on the top of this page, put in " PS3 HDMI ". The one that has the 10 solutions so far has the best answers for you.
Good Luck

SOURCE: Picture keeps alternating between HDMI1 "blank screen" and cable

try the lead in another slot and even another lead, if problem persists demand an engineer comes out.

SOURCE: 42'' lcd turns on no picture/menu

Your tv is being attacked by electrical surges which seem very violent and has already damaged some logic controls. Please invest in a AC filter which will protect your tv from such spikes....... but first you need to get your tv serviced from the electrical damaged it has already suffered.

SOURCE: flat tv, sound but no picture. have tried

I had one that had a black screen and fixed the problem by repairing the inverter. When I opened the unit I looked at the capacitors on the inverter board and found them swollen. I looked at the bottom of the board and found that the fuse had opened up. The caps were a cheap quality low temp variety 150uF at 25V I replaced them with 330uF 25 volt 105C caps. I then replaced the 2.5A surface mount fuse with an axial 2.5A pico fuse and the TV worked beautifully.