This issue is being caused by Security updates on the Windows Server.  Uninstalling the update(s) will resolve this issue and return the font to normal.

If the server is 2003, uninstall Security Update for Windows Server 2003: KB3013455.
If the server is a different version, you can either uninstall all the updates installed since this issue started occuring, or the updates could be uninstalled one at a time until the font is back to normal.