To be honest I've never tried it as I've never had the need to, but I would try this way then. Sorry, this is the full document on it, perhaps you need to be in this menu first before you can reset - apologies but as I said I haven't need to try it out...let us know..
Humax Hidden Menus
To reach a 'manufacturer' hidden menu, in the STB Status menu, press
[red] [green][yellow] [blue] [white] then select one of the following options
0 - Reset pin Number
1 - Loader Download
2 - Application download
3 - Eeprom data download
4 - Channel data download
A dialog box confirming the selected option should now appear.
I have also heard that the following will reset EVERYTHING on the hummy try the following [Mute],[3],[7],[1],[7],[5].