[AccessD] Queries suddenly not updatable?

I've got some update queries in an app that I run using DoCmd.RunSQL. These
queries have been working successfully for years, but now suddenly I'm
getting an error message that says I must use an updatable query. The really
odd thing is that I recreated one of them and saved it as a named query, and
it runs fine. I've tried compact and repair without luck.

Has anyone got any idea what may have caused this, and how I can fix it?

TIA,
Arthur