I've tried to duplicate your problem using a newly created project. After getting some initial entry information entered through the data entry I checked to see what the repeat would do. As this was a clean install of TMG8.06, there were no repeat values for any field, even after the initial data entry was complete. As soon as I created and completed a new tag entry though, any subsequent entry had repeat values available.
Have you looked at your files in the UsersxxxxxxDocumentsThe Master Genealogist v8Repeat_files directory? When you add anything does the time stamp of the Repeat.DBF, Repeat.FPT and Repeat_S.DBF change? If you click to see the properties of those files does your account have permissions to make changes?