I have this type of problems and litterally ran out of ideas. Yesterday was playin with my reprap with ramps 1.4 when accidentally after touching one of stepsticks connected lcd stopped working n turned blue, like there would be no program loaded. I am addin post on arduino forum because i am actually tryin connect with my arduino mega and it won't response. Both LEDs are ON when i plug into computer but PC doesn't seems to see this arduino. Don't know what could happen. Maybe there was some kind of short circuit but everythink looks fine. I was tryin joinning arduino on different PC and ports. Device manager also doesn't see arduino. Is there any chance that arduino can be damaged despite working LEDs ?