I have the Humax 5400 rather than the Humax 5400Z but I think that both boxes are fairly similar apart from needing different loader and update software.
1) Check your ToH version. It should read something like:
+Cam ToH3.3 plugged HoT5.7 (or similar)
This can be checked using your remote control and selecting:
Menu / ToH / HoT
You then can decide which version you wish to upgrade to - say:
2) To update your Humax, you will need the correct loader and 5400Z software plus a RS232 cable to connect from your computer to your Humax.
Assuming that you have done this correctly and clicked on the button on your PC to send the update to your Humax, you need to power your Humax down and back up to start receiving the update. If you have done this correctly, you should see a box on your TV screen showing the percentage of the upload received. When it reaches 100% and it tells you that the upload is complete you should press the "Standby" button on your Humax. The Humax should then return to a normal TV picture.
Using your remote control as described above, you can check to see if the software has updated.
3) You should be able to update your key files three different ways:
a) Download your existing key file from your Humax, alter it and then upload the altered file back to your receiver.
b) Obtain a new Key (Bin) file from the Internet and over-write your existing file.
c) Using your remote control select:
Menu / ToH / Parser / Ram Editor
Use your remote control to scroll to the key that has changed and key in the new keys. Your colour keys on the remote double up as the letter keys needed for Hex entries.
The last 5/6 versions of the ToH / HoT software have allowed you to use this method.
4) To update your Key (Bin) file using a file from the Internet,you need to have:
a) a RS232 cable connected from your PC to your Humax
b) DSR9500 Emu Editor v4.5 or later software
c) an up-to-date Bin file for a Humax 5400
Open the DSR9500 software and load the Bin file and then click on the "Write" button. The update should then upload to the Humax without you having to perform a power down/ up operation.
You can check to see if the keys have updated using the method shown in (3c) above.
5) If your selected channel is still not clearing it may be because:
a) The HoT version is not up-to-date
b) That package cannot be decrypted (changes on a day to day basis)
c) Your PMC Table is not up-to-date
d) The key file doesn't contain the correct Key.
I hope that this is of some use.