Here's my dumb photography thing (some of you will get this one): I put on my Lumiquest flash diffuser without returning the 580ex wide-angle flash filter back into it's slot. I'm firing and wondering why: 1) My photos are not exposing correctly and 2) why the hell is the display on my flash blinking?
Moron. It blinks when you're doing something moronic, moron. In this case, the wide-angle filter was pulled out and the flash was aimed vertical.

Luckily i realised what i was about to do and stopped.

