jquery Autocomplete in IE6: scrollbar overlap

jquery Autocomplete in IE6: scrollbar overlap

Hi,
I habe an Autocompleter in a form and below the Autocompleter-Fields there are two html-select fields with 18 lines height.
In Firefox there's no problem, but in IE6 the scrollbar of the Autocompleter field appears is behind the selects below (overlapped).
I read, this is because IE ignores z-index for formfields. Is there any chance to have a fix on that?
Scriptaculous is using iframes for the Autocompleter in IE, but there IE triggers onClick on the scrollbar and the Completion-Field just disappears, so you are unable to scroll with the mouse.