Happened to me a lot! Its the one called "structural wing" (now structural wing type A) It happens when I quicksaved/loaded a lot, and as soon as I return to Kerbin from where-ever. It can happen in space around Kerbin, or it waits until you approach the KSC. If i try quickloading, the structural wings will start expoding(poof!) again. It's usually solved for me by restarting the game and then resuming the Kerbin landing. What's funny, it never happened on my old computer!