Studio 2015 and MS Office 365

Last week I had to upgrade my MS Office package to the 365 version. Since then, when I try to confirm a segment I get an error message: "Unable to locate if Microsoft Word is installed on this machine". When I go to File > Options, Word is listed under File Types (see below):

I would appreciate anybody's help in troubleshooting this issue. My OS is Windows 7 64-bit. I use Trados Studio 2015 SR3.