drop-down issue: static vs. dynamic PDF

After saving a form designed in LiveCycle 8 as a static PDF and then opening it in Acrobat Pro 8 or Reader 8, I can type in a drop-down field and find selections by their first letter. If I save the form as a dynamic PDF, the drop-down does not find selections when I type.
I have compared the static and dynamic drop-down fields in LiveCycle, and I don't see any differences in their settings. Has anyone else encountered this?
Thanks...