I would be checking the connection with the flash, not switching lenses, I have issues infrequently with my 50D and 580EXII. I simply switch both off reseat the flash and that tends to take care of the issue... Bad Canon!!!
Andrew Rodgers
Perfected Perspectives -- Photography by Andrew Rodgers | Andrew Rodgers (acedrew) on Twitter | Login | Facebook
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Canon 50D 24mm, 50mm, 100-400mm, 28-135mm
Panasonic Lumix TZ-3 Yeah, I have optical image stabilization and a 10X lens, it also fits in my pocket.
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