I have a 580 EX II that I got when they first came out last year. I've been using it relatively heavy, but not everyday 24/7 type use. If I had to guess, I'd say it probably has 5,000-7,000 actuations.
What the problem is that it doesn't fire all the time. The pilot light indicates it's ready to fire, but when the flash is on-camera sometimes it flashes, sometimes it doesn't. As of late, it's not flashing more than it's flashing. What's weird is when it's "not flashing"- it actually is, but the light coming from the thyristor is very, very dim and not noticeable unless you were looking right at the flash.
Pushing the pilot button does trigger the flash, however. I have the flash set to fire at full power when the pilot is pressed. Most of the flashes are firing at full power, but some of them, just like when the camera triggers the flash, the thyristor is very dimly lit.
I tried different fully-charged batteries (to make sure a bum battery wasn't in the mix), I cleaned the contacts both on-camera and on-flash with alcohol (slightly dabbed on a q-tip) AND a pencil eraser, and I also did the DIY fix to take the hot shoe mount apart and I made sure all the screws inside the locking mechanism were tight.
To make sure it wasn't the camera, I mounted my trusty old 430EX and it fires 100% of the time and works perfect.
This flash has been working 100% fine for over a year and has only been acting up within the past few days. What do you guys think is wrong? Is a trip to Jamesburg needed? (I only live 50 miles from the Canon Jamesburg facility).


I brought the flash in for repair (I need the warranty card in order for the repair to be free), the 16-35 for calibration (free), the 85 1.8 for calibration (free), the 40D for a sensor and general cleaning/calibration (free), and the 1D for a sensor and body cleaning/calibration (out of warranty- 190 bucks but I have a voucher for 100 bucks plus 20% off parts/labor). Here's some pics:

