Wait, you installed FreeBSD to run the LiveCD, or you're running FreeBSD from the LiveCD?
If you're running it from the LiveCD, then that's because you're running it from a LiveCD, which is an .iso image on a CD and you cannot change it -- it's been burned into it. This behavior is the same in some Linux distributions (for example Slackware or Gentoo), where the system doesn't get loaded into the RAM, but stays put. If you want to try out FreeBSD without installing it, try VirtualBox. So, in short, there is no error, you cannot change .iso images on the CDs.
