Office 365 includes a Quick Repair option to fix install issues -- handy if the program starts behaving erratically. The Office IT Pro blog has an overview of how to automate the tool for large deployments.
One scenario where that might prove necessary is on systems which had an earlier version of Office installed, which can confuse file associations and result in the older version launching when users double-click on a file. Hit the post for full details.
Automating Quick Repairs in Office 365 ProPlus [Office IT Pro Blog]