I don’t know why, because I am not  a coder,  but sometimes you innocently put things into labels and the Moodle Gremlin takes advantage and steals your editing icons. It might  be some code, some javascript, a swf file -whatever it is, it causes panic , all the more so if it happens on your Front Page and the whole world could see you broke your Moodle. I know  – I speak from bitter experience…   There are some step by step instructions in the  Moodle docs but here is a screencast that hopefully will demonstrate how to get back editing rights and defeat the Gremlin. (And thanks to Dan P for helping me sabotage my front page!)