This does not happen in any other file nor any other field on the same computer?
quick fix might be to disable the spell check on that field. But I have to wonder if the file itself may be damaged. See if recovering makes any difference.
Are you using Bitdefender? It has a habit if doing this to Filemaker.
What is really interesting, that when I load the same file on the different PC - it doesn't give me that error. I use the same OS, same Antivirus (NOD32) and more/less same programs.
just saw this answer and am thinking that might be the solution to the dictionary problem I am having with some machines on our team.
Could you elaborate?! exclude FM files from bit defender? get rid of Bit defender?