I have read that this is a fairly common problem with these SAMSUNG refrigerators. Came home from vacation a few weeks back to find everything warm in both freezer and refrigerator compartments. Found evaporator coils completely frozen over. Coils defrosted when I unplugged unit and was cleaning out all the lost food - after plugging back in everything worked o.k. but coils will re-freeze about every 4-5 days (I'll unplug, defrost manually and go through it all again). Seems like unit is not going through the defrost cycle correctly, but I haven't gotten much help / advice from the folks at SAMSUNG (unit is about 4 months out of warranty). I have read on some posts the most likely cause is the PBA main circuit board, but wondered if I should start with replacing some of the lesser expensive potential culprits / parts first. Any advice is greatly appreciated (also, is there any special procedure to replacing the PBA main). Thanks for any help.