Form macro returning 'ole server' error (1 Viewer)

[Mist]

I have a form macro which has been working perfectly, until now. All it does is concatenate two fields into one using the 'setvalue' command. The ole server-type error is shown here. Any suggestions? System configuration?

I reverted to a few backups previous to this and I get no error but I would like to avoid having to redo all the development since!