Ajax and Assets

I'm getting double rendering on a page with tabs. Firebug says there are two AJAX calls being made: one to my controller, and one to assets.

What would cause this?  I've not used assets yet, so I'm ignorant on this topic. Would the asset call have to be explicitly done by the tab code (I don't see it there, but I might be missing it), or is it implicitly done as a result of something else?

Not sure what's this. What does the call to assets look like?

I don't know where it is being called in the code, which is part of the problem, but here is what Firebug shows as the two calls: