Ok I found the solution in another topic. The render at client option in renderPDFform service must be set to no. So the highlight works now with reader 8.1 in workspace.
Edit: The form is no longer dynamic if I set this option so the problem is still there.
In Firefox 3 with reader 8.1, the highlighted fields works fine.
So the problem is with the combination of Internet Explorer 6 and Adobe Reader 8.1.
Are they people who apply usage rights to the render process to a pdf document and display it in workspace with Internet Explorer 6 and Adobe Reader 8.1 without troubles ?
One thing to try is to remove the Form Augmenter service in the Default Render process, and explicitly add the Form Bridge component (on the Custom Objects tab in Designer) to your form.
I remove the Form Augmenter service in the "Render PDF Form ES Update 1" and add the Form Bridge component in my form. I'm not use to use this object, I just drag and drop the object into the form, is there anything else to do ?