There are Windows updates that disrupt GN4 functioning.

•Update KB2753842 causes an error when opening a page that contains text converted to curves::

"Unable to convert text to shape. Font error"

This is related to the Microsoft update KB2753842 that causes some Windows fonts to have an unreadable shape. The update is available since December 11th, 2012.

The problem is at Windows level and it affects all the Windows applications that uses the shape of video fonts.

The only solution available is to uninstall the update KB2753842.

Check http://msdn.microsoft.com/en-us/library/windows/desktop/dd144891%28v=vs.85%29.aspx in the "Community additions" section for more details.