|Upgrade in progress|
|Firefox in Breezy with font issues|
~$ sudo apt-get install ubuntu-desktop
It seems quite a significant number of packages weren't installed during the upgrade process. After everything installed Firefox went back to normal. Update Manager alerted me to an update for yelp so I installed that too, just in case.
It's not too big a trouble to fix, but inexperienced users probably won't have a clue how to try and fix things. Even I only tried installing ubuntu-desktop out of a wild guess. Thankfully, those days are far behind us. The upgrade process nowadays is much more robust than it was back then.
Next: Upgrading to Dapper