Notepad won't read it. Word or Wordpad should. Be sure the file has a .RTF extension on it. If not, you may need to reboot your computer to correct any problem. Sometimes Windows memory gets messed up, which can cause a problem with any application program, such as Hoster.
When in doubt about why something is not working correctly, aways turn off your computer for at least 10 seconds, then start it back up again. Maybe you did, but didn't mention it here.
