Users see duplicate category tiles (e.g. "Firewall", "General Services" are showing up twice, one on top of the other) in their Service Catalog homepage "catalog_home".
With the information available to Support (as the sys_portal_page and sys_portal pages are not audited), it appears that the reported double entries were created by a specific user.
This does not mean that this user actually caused the issue - rather, that due to lack of auditing (and thus lack of information), that was the last username associated with the changes made to the "Catalog" portal page ( ref: /nav_to.do?uri=sys_portal_page.do?sys_id=453809e40a04bfde001fb14e5729693d ).
By matching the sys_id's of the duplicate categories to the "dropzone" entries (see the "Portal" Related List in the above sys_portal_page), you'll see that there are duplicates in the dropzone list (e.g. "Firewall", "General Services", etc).
This deletes the duplicate "dropzone" entry and will cause the page to render correctly. Reloading the page will show the changes have been applied.