Thanks Randall.
I'm going to try workaround 3 to solve this problem but I have to obtain admin permission to do this first. It would be great if Esri could provide a built-in solution soon.
Workaround 3 - Replace GlobalUserInterface.CompositeFont
Replace corrupted font file with correct version.
Download GlobalUserInterface.CompositeFont (default download for Windows 7 is %USERPROFILE%\Downloads).
Open cmd
and navigate to %windir%\Microsoft.NET\Framework\v4.0.30319\WPF\Fonts and run:
xcopy /y %USERPROFILE%\Downloads\GlobalUserInterface.CompositeFont .
(or copy and paste the GlobalUserInterface.Composite file through Windows Explorer to %windir%\Microsoft.NET\Framework64\v4.0.30319\WPF\Fonts)
Open cmd
and navigate to %windir%\Microsoft.NET\Framework64\v4.0.30319\WPF\Fonts and run:
xcopy /y %USERPROFILE%\Downloads\GlobalUserInterface.CompositeFont .
(or copy and paste the GlobalUserInterface.Composite file through Windows Explorer to %windir%\Microsoft.NET\Framework64\v4.0.30319\WPF\Fonts).
Re-launch WPF application.
Reboot machine and re-launch application if you still have trouble.