f3 freezing

Hi all
I have recently replaced my sky HD box with an f3 sky box,
The picture quality on the sky box was superb,
However my f3 box seems to freeze a lot for a few seconds every 5minutes or so, I also get the message program scrambled
The signal intensity 90%

The signal quality 75%

I'm using sky broadband

Any ideas what the problem might be

Thanks mark