Pardon the re-post... Without warning or cause, the down arrow on my wired aluminum extended keyboard doesn't work. (All other arrow keys - heck, ALL other keys - work fine.) It hasn't been exposed to anything (e.g. fluids) nor has there been any software updates or special apps installed that might affect this. And, yes, I’ve reset the PRAM. I popped the key cap off and blew out dust, etc but no luck. All other keys work fine. I don't see screws to disassemble and clean it (unless they're under the pads). Can this be disassembled? Any other suggestions? Thanks!