You can try using this cables.xml instead of the 1 in the image (I can't remember if it is the same or not).
First you need to telnet into your box, and then use the command:
Then ftp the file to /etc/tuxbox and overwrite the existing cables.xml file
Then in telnet use the command:
Once the box is up and running again, just double check the tuner settings are still correct, then try and do a scan and see if it finds anymore channels.