Suddenly you cannot open attachments in your Outlook (2007-2016) – what is the matter now?
Your PC probably recently got updates for Microsoft Office, and Microsoft haven`t done good job with some of the recent patches for Microsoft Outlook.
Go to Control Panel | Programs and Features | from the left side of the window choose View installed updates
Search for some of the following patches according to the Outlook version you use
Outlook 2007: KB3191898
Outlook 2010: KB3203467
Outlook 2013: KB3191938
Outlook 2016: KB3191932
When you find the problematic update – select it and choose Uninstall from the top of the window.
After you successfully uninstalled problematic update – reboot PC and now you should be able to open attachments in your Outlook as you could before.