The overlay iframe in the datepicker (.ui-datepicker-cover) does not appear to be sized correctly in IE6 allowing windowed elements to bleed through the right and bottom edges of the datepicker control when used as an input popup.

I have tested this using the default theme, with the bulk of the code being provided by the jquery-ui-themeroller.zip from that theme.

You should be able to see the problem at  http://jquery.abldev.com