Combobox don't appear in the front of an element

I have a User Control 开发者_开发问答with a 2 (two) combobox. They work fine. My problem is, in a .aspx page, when I click in the combobox of the User Control, to expand the combobox, the options of these combobox appears behind of the element of the .aspx page.

The element, that appears in the front of the Combobox, is a <object> element (flash animation).

I found in the internet, some answers to this problem, like, set the wmode to Transparent or Opaque, but doesn't work.