Help! My client is mightily mad. They have people using versions 7 and 8 or Reader who can't use the forms I'm creating on ES2. I've enabled reader access and I've saved them as being Adobe Reader 7.0.5 enabled - so what on earth else am I supposed to be doing???
I am using LiveCycle Designer ES and experienced same problem. Generally in some forms backward compatibility creates an issue. Some of the functionalities of the form is not literally understood by some old versions. If you see the default compatibility set in LiveCycle Designer ES is 8.1 or later. It might not work in earlier versions. But the most difficult part is to understand which functionalities of the form responsible for this.