Firstly, switch off the unit at the rocker switch at the back. Then remove the aerial from the PVR and then power it on.
Access your MENU>INSTALLATION>DEFAULT SETTING>YES (your password is '0000' when required)
The unit will now turn itself off and on again.
Once the machine turns off you will need to reconnect the aerial.
This will reset your box and rescan the channels (you will need the aerial reconnected at this point), once this is finished, make sure to SAVE the results, and this should resolve your problem.
Note: it doesnt delete any recorded shows.