Gordon,

Yes. This actually is a long standing bug from the javascript function. If you had selected a forum in you MyForums list which no longer exists the function looks for it and doesn't see it in the list and spews the error.

The workaround is to deselect all chosen forums and then select from those available. This should fix it. In the meantime we are completely rewriting the MyForum selection tool so it doesn't use any JS.