It's possible the ribbon connectors on the bottom of the panel that plug into the address driver board need to be reseated but more likely you've got a bad PDP panel.

Sorry.  

I have a vizio P42HD with a 2" black vertical stripe (with thin bright line down its center) down the left third of the screen, and two colored stripes down the right third of the screen.  Also, the color shows a lot of bleeding and appears overdriven.  Any ideas whether it is economically repairable?

I had the same problem with my P42hd.  I had a red, green and purple stripes in my screen.  I tolerated it for a while until the left side of the screen went total black except for the stripes.  I have opened the back and used can air to blow out the dust that had accumulated over the years.  After which plugged it in and turned it on and only one stripe remained.  However, the problem with the left side still not showing a picture.  I believe my problem to be an open or a short somewhere because when i twist the frame a little, the picture comes back.  I am going to open it up again next week.

A word of caution.  Just as MOtvguy mention "its only a possibility."  I have a few years of electronics repair behind me.  If you open the back be aware of the high voltage capacitors that may still be carrying a charge.  Ensure you have a grounding probe available to check and discharge the circuit before touching any circuitry.

Please email me if you have anything else to add.