var ddCtl = $find("MyDropdownControl");
if (ddCtl)
{
    var items = ddCtl.get_items();
    for (var x = 0; x < items.getLength(); x++)
    {
        var item = items.getItem(x);
        item.set_disabled(false);
    }
}

No matter what I put in for a value in set_disabled() true or false, the disabled css class is used to format that item (DropDownItem Class Members )

Also, as a DropDownProvider for a WebDataGrid, 2 issues:

• The dropdown does not drop down in FireFox 3.08, it does drop down in IE8 regular and compatibility mode (I've read the other posts on z-index for FF - haven't tried that yet)
•  In IE8 regular (compatibility mode off), the positioning of the dropdown is horked when you scroll the webdatagrid

Thank you!