Took backup of a Lesson on 1.5.4 and restored to 1.6.4 localhost. and then to a 1.7 locahost Helen accepted my help with a demo lesson, so I restored it to a 8 hour old version of Moodle 1.8 on a localhost. Looked at it did some edits. Then uploaded to Helen's /dev/moodle18 website. I was too busy with content and was only went Sally Student tried the lesson, she noticed she could not advance beyond the first branch page.
A grey box appears. Questions seem to work. Edit of Branch Tables work. Changed lesson setting for position of branch table buttons. Check the copy on my 1.7 localhost and the buttons are there.
There are a few other things I noticed but I will put it on another tracker.