Collapsed fieldsets containing sticky header tables won't display table when expanded in IE7

Well title is quite a mouthful, but I discovered this using the "Node Privacy By Role" module for Drupal 6.

That module implements its form elements within a table (which is created as a sticky header table by Drupal 6 because there is a header) that are in a fieldset that is collapsed by default. While it worked in FF, IE7 will expand the fieldset but the table that should be inside is never rendered.

If you set the fieldset to be expanded by default the table is displayed.