Problem with 2 DropDownLists

[Jorge]

I don't know in what case can this happen.

I have to WebUserControls (CompositeHeader1 and
SubcategoriesList) each one have a DropDownList
(ddlCategories and ddlSubcategories respectively).

the clientID for them
are "compositeHeader1Ctl:ddlCategories"
and "subcategoriesListCtl:ddlSubcategories"

The problem is that when I select an option
in "subcategoriesListCtl:ddlSubcategories" the
ddlCategories.SelectedIndexChanged event is arised instead
of ddlSubcategories.SelectedIndexChanged.

I'v already reviewed the Page.Request.Form("__EVENTTARGET")
value and it is "subcategoriesListCtl:ddlSubcategories".

Any Idea??

Thank's in advance.
Jorge