Invalid annotation specified in annotation field

Unable to create a note, label, dimension, etc.

File -> Preferences -> Drafting -> Common -> Lettering -> Text Parameters.

Check the shown text  in the active file and make sure the font is set to the correct font.

Next, checked Appended Text, Dimension Text and Tolerance Text.

Make sure these are set to the correct font.

When selecting the box to change the font, and you get a warning message, the file selected could be corrupt.  

Note, by default NX is set to use the Windows Ariel TTF (True Type Font).

If the Ariel TTF is corrupt on this one machine, then it needs to be removed and replaced with a known valid version of the Ariel TTF.