According to Canonwatch, there will be a new firmware update for Canon EOS 5D Mark III this week, mostly like on October 31, 2013.
What’s new in this firmware update:
This update should mainly address an issue with the SpeedLite 600EX-RT not firing several times when you use manual setings and IR on.
via: Canonwatch
Reminder: B&H has two hot deals on 5D Mark III: Body Only + Printer + Photo Paper + Memory Card for $2,899.00 , w/ 24-105mm lens + Printer + Photo Paper + Memory Card for $3,499.00