I am having a similar problem.
I have a jQuery/css based vertical slide menu, and haveing PowerGallery seems somehow to force all the menu "kept unfolded", where only opened category area menu should be unfolded.
(See: shop_160_covers.php )
I tested with jQuery LightBox (similar effect with PowerGallery, but much simpler) to see if that triggers the same symptom, but it didn't.
I'd like to stick with PowerGallery, as it is easy to use, and it gives me sliding effect that I can not hand-code.
Could you take a look and advice me what to do to keep the menu folded?
Thank you for your help in advance.