All other programs? Normal. Mouse? Normal. Windows? Normal.
The cause? A known problem with an automatic update “fix.” If you face this same problem (after all, Word worked fine last night but not this morning), check out the Microsoft Help and Support site, where you will find the simple fix that makes it once again work fine.
The irony? Microsoft acknowledges this problem exists (see and click on the highlights). Why haven’t they created a fix for it that gets pushed out, as opposed to hoping people find the solution on their own?