It's playing funny buggers again, Jason. It was working fine. Here's a rundown of what I did, unknowingly recreating the problem in the process.
1. I went through steps 1 to 4 again, however I took it to the point where I created a 'results' page before I decided to 'finish' so I could save everything I had done as a schema. That way I could open it up again, continue working on this particular schema without risking all the work I had done.
2. Once I go back into the DataAssist wizard and select the schema I had been working on an error message comes up. It's attached but the general message was that 'formButton has no properties'.
3. I OK that (my only option) and go into the wizard to continue adding the two other pages I require ('insert' and 'update'). On working on the first additional page ('insert') it decides unexpectedly quit.
I'm now going through the reinstallation process as you had suggested.