Corentin,
Actually, it wasn't even highlighting the custom dictionary I had -- it was grayed-out. I had created it in "Documents" so that I could back it up easily. You got me thinking and Bill's question got me wondering....
Bill,
I had created a new dictionary using Word called "Karl's Custom Dictionary.dic" and Word wasn't objecting. Now that I look at it it's not clear it's been using it even though I'd point it to it. (I'll have to see where it is putting those things I've been adding.) So, I went an old dictionary I had on Windows and copied it into "Documents" and voila! I checked it by putting a misspelled word in through an email "Add". So, there was something about the name, perhaps, that it didn't like though by having a pointer to a file I'd assumed I could use any name I wanted to. Interesting....
Anyways, thanks very much to you both for asking / suggesting.
Looks like the culprit is: you can't use just any "mychoiceofname.dic" for this file.
Karl.