This happened to my mate with his 4X bike. He actually wore a hole in the frame..which then cracked, and snapped. - And that was from the tyre! similar... >_< Tape would do nothing really, if a rubber tyre constantly brushing past wore a hole in a metal frame, then a chain would tear through tape no problem! Your best bet is to do what Ash said, and get a narrower BB. Does look like your chain line is terrible, causing the chain to rub on it really badly! Thinking about it, what chain are you running? Could perhaps try a narrower one?