KB3013455 (MS15-010) causes font corruption
There are numerous pages in this thread on how the latest batch of Microsoft Security Updates have caused havoc on display fonts. In this case Courier was corrupted. Apparently the best fix is to uninstall the security update.
Surely Microsoft is pulling the update, but not for sure yet.
Microsoft needs to do a better job testing these updates and the unintended side effects caused by these updates.
There are thousands if not tens of thousands of people who are experiencing these issues.