In Knowledge search the category drop down box is not displayed fully

The Category drop-down box within Knowledge advanced search is displayed partially on IE 7, 8 and 9. When using Safari, Firefox, Chrome or IE6 this is not an issue.

Steps to reproduce:

1. Log in to HI using Internet Explorer 7, 8 or 9.
2. Navigate to Self-Service > Knowledge.
3. Click Advanced search.
   The Topic and Category fields are now visible.
4. In Topic, select Email.
5. In Category, select Web Mail.
6. In the Search bar, type Email and press Enter or Return on the keyboard.
   The Category drop-down is displayed partially.

There is no workaround for this Known Error at this time.