CiviMail WYSIWYG Doesn't Appear in IE

A client just came across this issue.

When creating or editing a mailing, on Step 3 (Mailing Content) there are options for HTML and Plain text formats. The editor windows look fine in Firefox (version 3.6.6). When I check the same thing in IE 8, I don't see the editors (see attached). Clicking the triangles to the left of each editor region doesn't do anything.

Thanks!