I have a multiselct / dropdown, which is populated from a UDT.
This works, but the multiselct does NOT RETAIN the visible selection, when you
return to the page.
ie :-It appears as if no selections have been made.

{content_module module="ECB" field="dropdown_from_udt" block="tagselect"
label="Select tags here" udt='categories'  size="50" multiple="true"
assign='tagselect' tab='Tags'}

Where UDt is :-

cms_utils::get_module('CGBlog');
$blogcategories = cgblog_ops::get_category_list(FALSE,null,FALSE);
$catarray = array_combine($blogcategories, $blogcategories);
return $catarray;