A couple of days ago some of our users starting getting this error when sending an email in OE:

OEWIN.EXE - System Error

The program can't start because MSVCR110.dll is missing from your computer. Try reinstalling the program to fix the problem.

It also occurred for one user in PO although that has resolved itself, however the problem in OE remains.

Any idea what's causing this or how to fix it?