Sorry if this is Off Topic but there is such a pool of knowledge here
that I'm sure someone will know the answer.

My mother's digi-box (Borders area are fully digital now) gets upset
when the adverts come on - it's fine with BBC 1 and 2 but seizes up on
the adverts on the other channels. I watched it yesterday and on the
first round of adverts it frame locked every so often and made a
clicking sound each time, but continued fine when the programme
material came back on. On the second round of adverts it locked and
didn't clear itself - would have done so seemingly if switched off and
on again. I changed it for another box and the TV was OK.

I've brought it home to play with but what is there different about
adverts on TV from normal transmission ?

Thanks
Rob