This is getting a bit crazy. I have been trying the code for hours now and no luck:
I had this issue recently, and the accepted answer did not fix it for me. In the process of creating a question on it, I figured out the solution:
When using both jQuery UI and jQuery Mobile, UI must come before Mobile in your list of scripts.
I had this:
Which resulted in UI having precedence over my form elements, especially noticeable in select menus. I switched these statements, and the menus were enhanced by Mobile properly.