Issue with 580 EX II

While trying to fire my flash off camera using my cybersyncs, my 580 wont fire. LCD is on, all other functions work, but when I press the pilot to test it, it flash head fires for about a full second then stops. It worked fine 2 days ago and I havent touched my set up since. Any ideas?

Upon further testing, the flash functions as it should while being used on camera, though a press of the pilot button yields the same results as above, and it will still not fire with my cybersyncs.

I think the cheapest options are to check the batteries, then check/change the cables. It also sounds like you have a bunch of Custom Functions set on your flash.

I was just typing this to my embarrassment. I indeed had the modeling light custom function set. Not sure how or why, but whatever. Thanks .