Thunderbird New Card panel has no Cancel or OK buttons
In Thunderbird 18.104.22.168 installed in Ubuntu 6.06 the New Card panel brought up by the New Card buttons has no Cancel or OK buttons at the bottom, making it impossible to make any additions to any Thunderbird Address Book.
Existing Cards DO have Cancel and OK buttons, but those cards are the result of an import via floppy from an earlier version of Thunderbird running in Windows XP.
Is this a bug, either in Thunderbird or Ubuntu, or a bug only in Ubuntu's version of Thunderbird? Or something else?