The Office 2013 Rollup Update KB2817630 is currently causing mayhem in Outlook land.
After applying it, the Folder Pane (aka Navigation Pane) shows up empty for some users. Clicking in the empty section will minimize it where you can then click on the “All Folders” button to see your folders again and also be able to reach your Calendar, Contacts, Tasks and Notes folders via the icons at the bottom (in case you have Compact Navigation enabled).
Apparently, they thought the Outlook interface still wasn’t white enough
As these are both hotfixes, you won’t see them in Windows Update but need to request them via their above linked KB page. For more info about the process, also see: What are Hotfixes?
Microsoft is in the process of re-publishing the September update so that applying the Hotfixes will no longer be a requirement. Until that time, if you don’t want to or can’t install the Hotfixes, uninstalling update KB2817630 is an alternative option. As this isn’t a security update, it is safe to do so.
For more information about removing updates see Uninstalling Outlook or Office updates.
Note: The update has been pulled from Windows Update so it will not automatically try to re-install itself anymore. When the updated release becomes available again, it will also be offered via Windows Update again even when you leave it installed.
Cause and who are affected
The issue is caused by an incompatibility between a specific version difference of outlook.exe and mso.dll, usually caused by not having AND at least one of the August hotfixes AND the September update installed.
This version difference can only occur when you are using MSI based installations, which are Office 2013 Standard and Professional Plus. The Office 2013 Click-to-Run and Office 365 installations are not affected.
For more information about the issue, check out the post on the official Microsoft Office Updates blog.