Did it just burn right around a solder joint? Is it a cold/broken/bad solder joint? There is a fair amount of stress on the horizontal components, and a cold solder joint, cracked trace or other bad connection will lead to arcing and burning. I've seen several cases of large burned marks on boards from something as simple as a cold solder joint.
Clean up the area, check for bad connections, and fix any you find.
-Ian