OK. I don't run 3.4.2 so I'm of limited assitance. You may want to enter your version number in your signature for future reference.
Have you tried looking at your database to see if the table this information is stored in has become corrupted? Check one of your database backups for the default value and manually enter it through phpMYAdmin.
That's all I can suggest. You did backup your database right?
Good Luck!
