If its actual picture inteference then change the output frequency. to do this press services, 4, 0, 1, select, 4. the output is set to ch68 by default but in some areas this is too close to ch4/s4c. change it to 22 and retune your **.
grundigs do go tits up sometimes after an automatic update, which was done a few weeks ago. to update and renew the digibox software yourself disconnect from the mains, press and HOLD the backup button on the box (not the remote) and reconnect the power. keep the backup button pressed and after about 15 secs all 4 lights will come on on the box and an updating message onscreen. leave for ten mins and the box will update and reset itself, leave for another few mins and then press the sly button on the remote.
job done!
i think the latest software version is
operating system 1.2S4Bc<br />EPG software 2.8b*
I'll verify this tomorrow and post again if im wrong.
hope it helps