I have the same problem in version 2.7. In my case I have two domains hosted at one.com. At domain A the format bar is working correctly, at domain B it is missing.
I have tried the checklist above, but this din’t solve my problem. I have uploadet all the content from the same local folder at the harddrive. Both uploads are complete installs and not upgrades. I’m using the same webrowser in both cases. Both IE an Opera gives the same result.