Don't use Chankast.
Chankast's CD-ROM emulation is finicky at best; either your disc image(s) are corrupt, the are not selfboot, or Chankast simply fails at emulating the CD/GD-ROM stuff properly (most likely).
Like I said, don't use Chankast. Why would you want to use something that's been dead for seven years and surpassed in every possible way by two/three other emulators?