Sweet - sounds like a bad row of pixels! Time for a new plasma.
(yes, I know, very frustrating)
As long as it is all under warranty, which I expect it is, then you need another new one. This is not a good sign of reliability for Panasonic.
On the other hand, usually once things work for 90 days, they tend to keep working for another 10 years unless hit by lightning. Just getting past the 1st 90 days can be a real killer.