Seems like to high a gain on set

Not familiar with your model, but the problem sounds generic. I am guessing your set is hooked to a cable tv box, and that is where you need to change channels. I also guess that when you changed channels on your TV you probably moved from channel 3 to either channel 2 or 4 and the cable tv box is not sending to those channels so you lose picture and sound. Now, more guessing, you try to put the channel back to 3 on your TV, but still nothing happens. OK, if close so far, there are a couple of things to try. First, be really sure you are actually going back to the same channel you started with. Assuming you don't actually have the signal coming in on an auxiliary line-in and that you had it coming in on a channel, you may need to reset the presets on the television so that it recognizes the one important channel the cable tv box is sending out -- just follow your television menu to select or set channels. There is one more possible easy problem ... I have seen this one happen, after getting the channel correct and reset, if it still doesn't work, you mght need to turn the set off and wait one minute, then turn it back on WHILE the cable box is ON. This can cause the set to RE-Latch onto the cable box signal. It really doesn't sound like something is truly broken or needs replacement, sounds more like a user error. If your set is still under warranty, just call the Panasonic hotline (find it in Google, and they may be able to walk you through exact instructions for your model). Hope this helps.

If you are using the TV's tuner and an aerial, the aerial has a problem , (one of the reflectors/elements has come off or is bent) or the tuner unit has gone low gain at the lower frequencies.
Have a look outside at your aerial. Or there is a poor connection in the aerial system.
Hope that helps

check and see if you have a zoom button on the TV remote
If your hooked to a cable box call the provider because some of the cable boxes have a setting that will cause this issue

This sound more like a cable issue. Also check the leads going from your cable box to the set/ If you are using component cables one of them may be loose.

Typically the cable box is the source of your channel programming. If you're getting the "no programs available" you need to find if that notice is from your TV or your cable box. Check the connections from your cable source to the cable box and from the cable box to your TV.
Make sure that your TV is set on the proper source selection. Most Projection TV's have several (ant, cable A, B, DVD etc) check your on-screen menu for which one and make sure the cable is connected to the proper input ports on the back of your TV.
If you disconnect the cable between the tv and cable box and still get the "no programs "...then it's your TV.. but if you lose that warning, then it's coming from the cable box... If after checking your connections, disconnect the power to your cable box and let it sit for 5 minutes and then reinsert the power to the box and see if you get a reset with signal...... If nothing after all this, contact your cable provider to check their signal to your house and also the cable box.... Hope you have quick success on this!

satelliteand cable TV is only comes in black and white.
this a HTML type plug or a coaxial
select menu and source
very weird... should default to colour

if no luck try plugging in a desk top digital box tune using that

TH-42PX20 TH-50PX20 Operating Instructions High Definition Plasma ...

ftp://ftp.panasonic.com/television/om/th-42px20_en_om.pdf

When ever the picture freezes intermittendly the problem is usually poor connection on the signal line (antenna or connection on tv) or poor reception. Could be the tuner if the tv has one.To eliminate the tuner possibility try anther tv set if possible.
If you still cannot figure out the problem,let me know what kind of set up you have connected to your tv set.
Do you have a satellite or cable box and if you have splitters.

it depends on what your using it for, adjust colour tones to what you think looks natural, contrast between 80-90, keep sharpness below 30. just have a play around till you find what best suits the source material.

Try this one and see if you like it!
Normal: No
Picture mode: Custom
Picture: +22
Brightness: +9
Color: -3
Tint: 0
Sharpness: 0
Color temp.: Warm
Color mgmt.: Off
C.A.T.S.: Off
Zoom adjust: (grayed out)
PC adjust: (grayed out)
-- Other adjust menu
Video NR: Off
3D Y/C filter: Off (grayed out)
Color matrix: HD (grayed out)
Block NR: Off (grayed out)
Mosquito NR: Off
Black Level Light
3:2 pull-down: On
HD size: Size 2

Normally, when I see this problem in the customer's home, I find the main culprit to be the cable box. The remote for the cable box may have a button on it to change the format or picture size. You may have to go into the menu of the cable box to change the format setting. Hope this helps.