I had the opportunity to use some professional flashes yesterday and I found out that they didn't fire when I was trying to shoot with the camera in Live View mode.
The flashes were two Elinchrom FX400, one wirelessly synchronized with the camera and the other was activated automatically when the first one fired (With a photocell or something).
Using the camera normally fired both flashes at the same time with no issues, but live view mode deactivated both. Why the LV mode is incompatible? Am I missing something?
By the way, I tried this with two cameras, a Canon 1000D and a 550D.