Oh, I just received an answer on the Pagelines framework forum about this issue. This might interest you too…
This is a very common thing. The plugin is using the same z-index as the drop down menu, thus interfering with the ability of the browser to display the drop list. You’ll have to ask the developers of AdRotate for a different z-index and the CSS code to change it, or, if you use Firebug for Firefox or Chrome’s Inspection Tools, find the z-index code for the ads and modify it in Custom Code.
I’m not sure about your proficiency with CSS, so please let me know how you get along.