I have the same tv and same issue. I too was told it would be 300.00$ to fix. I did find the replacement power panel at partstore.com and encompassparts.com. the board is bn44-00161a. I have not purchased one yet, I want to see if there is another way to fix without replacing it first.
Have you fixed yours yet, if so what did you do.
2 years ago I purchased my Samsung HPT4254, and this morning I turned on the tv, and after 5 minutes it shutdown and kept clicking as if it were powering on. I removed the shell, and took out the power supply to look for blown circuits, but I didn't see any bulging. I had a samsung technician come out, just to have him tell me it would be $300 to repair, but all he told me is that it was the power supply. Can someone please give me an answer as to what to do, and what this white gunk looking stuff all over the power supply is? It look almost like white gorilla glue.
I have pictures of the power supply, and a video of the white gunk.