Lyndel thanks for your comments. I have fixed the problem but may take a look at the old file anyway.

Decided it was easier to create a new activity, copy each page from the offending activity into the new activity doing a download test each time. I then deleted the old activity and renamed the new one to the same name as the old one. It fixed the problem. A few jumps here and their to fix - in the end only took 20 mins or so.

It seems that in migrating from V1 to V2 of Prontoedit two virtual buttons were created (ghosts or what ever you might call them). Anyway problem fixed.