Acrobat Form issue: 'The Font '****' contains invalid encoding. Some characters may not display'

I have a 2 page PDF form that is getting this error message every time I open the document.

"The font "HelveticaNeue" contains an invalid encoding. Some characters may not display."

The document has been in use for a year (never having this error message) and needed some updates. All that was changed was the addition of some extra fields and some options in one java script to reflect extra addresses in a drop down menu.

HelveticaNeue was in a PDF layout (from Illustrator) for the background but this variable was removed when I converted all fonts to curves (outlines) and replaced it in to my form. Under Properties>Fonts HelveticaNeue isn't even listed. All fields are Myriad Pro (triple checked) so I cannot understand how it is still an issue. It does not seem to have any impact on the document apart from the error message. It is hard to remove when it does not appear anywhere in the document except for the error message.
 
Any help would be appreciated as I would prefer to not have to start again from scratch.