Can anyone help solve this frustrating drop down bug in Adobe Reader 8?

Question

Has anyone encountered drop downs in their PDF form that don't work in Adobe Reader 8?
A simple example is my form (stripped back) here:
http://www.wikski.com/misc/test.pdf
I've built a form with 22 sections in it, some 1800 lines of code, and now every single drop down has decided to not work in Adobe Reader 8.
The behaviour is when you select a drop down, it immediately deselects itself and you can't use the element at all.
I previously had this occur, and by simply deleting the element in LiveCycle Designers ES2 (which is what I've used to create the entire form) and recreating it exactly the same; seemed to fix it. However, I am so far past the point of being able to recreate every drop down this time, I need to actually know what's causing the bug.
Any help would be greatly appreciated!
Cheers,

Answer 1

xfa.layout.relayout(); is required to re-render the entire form in order to have the field change color on Enter event. Without this, the field won't change color in Adobe Reader 8, this goes for all fields not just drop downs. Instead it'll just flicker the color change, xfa.layout.relayout(); makes the color change stick.
Thanks for your help, I've decided to take the set_focus() event off drop downs and keep it in place just for other field types such as the text input field.