Jim,
I have owned the FX-4A for almost a year now, I have never seen that error message. I wonder if you have a newer or older firmware than I do. It does sound like high SWR to me. BTW, I really like my FX-4A and use it everyday. I also have the LD-5 which just sits on a shelf. The LD-5 is nice and all, I just prefer the form factor of the FX-4A better.
Joel
KB6QVI