I have not seen that issue with any IQ in our inventory or heard from any customers with that issue.
On any issue like this I'd call your dealer. We (the forum) can certainly help, but half the advice will be well-intended-but-wrong and all the advice will come somewhat piecemail. Working with your dealer by phone (or in person) means you can easily step through a series of troubleshooting steps based on the results of each step.
Here are some of the questions I would think your dealer would want to know the answers to:
Did you follow the instructions to remove the back from the body before updating the firmware? Were there any error messages during the firmware update? Were you running 2.x before the update to 3.x or did you upgrade directly to 3.0 from a lower firmware version? Did it do this right away? Does it do it all the time or just some of the time? Was it like this from immediately after the update or did it only start happening at some point after the update?
If you don't have a dealer you can easily reach on the weekend here are a few troubleshooting steps you might try (listed in no particular order):
- reverting to the previous firmware
- restoring defaults
- reformatting your CF card
- trying a different CF card
- re-installing the firmware
- restarting the back
- trying a different battery*
Since you're the first person to have this issue as far as I know it's hard to say for sure, but my gut feeling is the CF card (compatibility issue or improper formatting) is the most likely culprit. Major improvements were made to the CF read/write in this firmware. But that is just a guess.
In general I don't suggest updating firmware right before a shoot; especially with Phase One I've found very few glitches with firmware updates, but of all the backs out there it's inevitable that there will be at least one - and Moore's law is it will be one that is about to be used in a shoot!
*yes I know this one is a long shot, but then again your problem is not an issue I'm aware of with anyone else, and I'm always willing to accept strange answers to unique problems. For instance if your battery is damaged/deficient/inconsistent it could effect the graphics board under 3.0 firmware but not cause issues in 2.0 firmware. Though to be clear this is one of the least likely explanations I could think of.