If you're using Mekko Graphics and the drop down menus on the right click are blank (see above) or frozen, this is caused by a compatibility issue with some versions of Office, including Office 365.
To fix this in PowerPoint, select "Optimize for compatiblity" Under File > Options > General and then close PowerPoint. Restart your computer and the right click menus should appear.
If the problem occurs in Excel as well, you can solve it by unchecking the box for "Use best settings for my display" under File > Options > General and then close Excel. Restart your computer and the right click menus should appear.