Hi,
what you're talking about does not sound like a weekcalendar issue, as dropdowns are not packaged with the plugin, it looks like it comes from the way you display the dialog.
I guess you add times to the dropdown everytime you show the dialog aren't you ? in such a case, clean the values first.
If I misunderstood what you're talking about, write back and link to an example so we can understand better your problem.
Julien.