I assume you only see this on the admin page?
It could be caused somehow if you’ve tried to add a custom font of your own. Have you done that? Did you try to delete a font?
I’m not sure how things could have been corrupted, but it may be true. If you could use the Weaver Xtreme Plus Admin X-Plus Save/Restore to create the “Save ALL Settings” file, and send that file via e-mail to weaver at weavertheme.com with a reminder of why you’re sending it, I could see if I can reproduce the file. It is possible that there is some bug when adding / deleting custom font sets.