Font navigator issues

Every time I use a font navigator, weather it be Bitstream that was installed with Corel Draw x7,, and now Nexus font navigator, it changes and deletes some fonts. Now it has changed Arial (as default) to something else. I have reset the default but it does not "save as default". I'm using windows 8.1, it did the same thing on my windows 7 computer also.

Thanks 

Mike