My 52" Toshiba DLP just dropped an HDMI connection... There are two connectors on the back, both have worked fine until just now when one disappeared from the inputs menu on the screen.

Your problem is in the streaming player. It is not keeping up and when an HDMI loses connection it will not auto find it again. To verify this take the Panasonic out of the loop and see if this fixes it. I love HDMI but it is touchy

Have you got the Auo Aspect setting turned ON in the Picture Menu?

What is the Model Number that is Printed on Back of TV?

Most TVs choose the resolution based on the signal coming in. Be careful if you try and use 1080P. Not all TVs support it. 1080P is only on HDMI. set the playstation to 1080i before connection.
Some TVs and Playstation HDMI do not mix well due to software in the HDMI ports. Try RGB cables.

Could be a bad lamp.

Have the tuner signal board replaced. HDMI does not use the regular tuner bands, it is bypassed when using hd inputs.

I contacted Toshiba and they said to turn the TV on first, then turn on the HDMI device.

This happened to me many times with my Sharp 40" LCD. I am actually running 2 tvs of of 1 HD Tivo. One in the bedroom with HDMI and then through the wall into my kitchen tv via Component. ( yes whatever is on in the bedroom plays in the kitchen).. So this AM my power dropped out for a few seconds then came back on. When the Tivo rebooted I got that " hdmi connection not permitted" message. In the past, I would just reboot everything and all would be ok.. But today I couldnt get the tv with the HDMI to display the programming. It would show the tivo menus, but when I tried to play anything or watch live tv, the message would pop up again. The kitchen TV with the components was working the whole time...
So finally I rebooted the Tivo one more time. But this time I left the HDMI cable unplugged from the Sharp in the bedroom untill the Tivo was fully booted and a live channel was playing in the kitchen. I then plugged the HDMI back into the bedroon TV, and it came back on. Im not saying this will work for you, But its worth a try

Have the input signal board replaced. Might try also replacing the digital board assembly.

This is a wild guess, but I believe that you are being **** by the movie industry. The HDMI protocol includes a form of DRM (Digital Rights Management) for high resolution content called: High Bandwidth Digital Content Protection Basically this means that the media (disk or broadcast) instructs the player (in your case the cable box) to insist that any downstream devices (your TV) is industry and DRM compliant. Specifically this evil protection scheme is designed to plug the analog hole and make it impossible for you to record or copy the movie by using an analog output from your TV. This even restricts the size of the TV you can play the movie on, thus preventing pubs and bars from displaying the content on big screen TVs without paying royalties. The message means that the manufacturer of your TV has refused to toe the industry line. 1984 Anyone ? Martin