Please would you add a bit more detail.
Are you connecting a 9300T by HDMI or a 9150T, 9200T, 9300T by SCART?
Which model have you got?
If you have a 9300T does it malfunction if you use the other type of connection?
Have you checked that the HDMI/SCART cable is connected OK at both ends?
Have you tried a different HMI/SCART cable in case the one you are using is faulty?
Have you got something you could temporary try out in place of the Humax to see if the problem is the fault of the TV and not the Humax?