I've been trying to resolved this for many months with the company that runs the site, but so far they're as bewildered as anyone. What they asked today is that if anyone who gets that error message could please take a screen shot of the error message and then forward it to me, I can then send it to the company.
Mind you, I don't expect anyone to take a screen shot of any error message. Just saying that if the error box does pop up, and you are able to take a screen shot, it could possibly help resolved this. Though even that is in question.
Fortunately, the error message doesn't occur too often. Just more often than it should.