I am having the same problems with my 51 inch Samsung Plasma TV. And Samsung refuse to do anything about it. There is a link: http://forums.cnet.com/7723-13973_102-551708/samsung-51-inch-plasma-internal-screen-cracks/. Look this up and you will see that we are not alone.
I have an internal crack on 51" Plasma rejected twice by Samsung. It is a star type crack on the inside of the screen and there is no outside damage. I have submitted this two times the first was transaction number 4117533904, which was quickly rejected as physical damage. This was determined by pictures and there is no way this could be determined by pictures so I called again and this time with transaction number 4117591339 which went to the executive board and was also rejected also by pictures as physical damage. This time they did have a Tech come by to look at it and he said that it is a gas build up in the screen and it will crack it from the inside. So far they have rejected it but last time I talked to the Support guy he had to go and check notes and did say that Samsung would pay for tube but not labor which is not acceptable as this TV is still within the warranty period and was a defect not physical damage. After looking on here the problem seems to be quite common.