I encountered this problem which started a few months ago. I started to get this message for a couple of channels, and this problem coincided with a very wet and windy night so I initially thought that was the cause of the problem.
Over a period of a few months more and more of my channels showed this message on my Sky HD (3 year old Thomson) box. I'm in a flat and no other neighbours seem to have this problem.
Anyway, I chased this up with Sky and initially they said that as my box was out of warranty they'd put my call through to 'Sky Protect' - the choices were £65 for a one-off engineer visit or £8.25/month for 12 months for insurance (including my router too), and I begrudgingly went for this option. The Sky website had informed me a month beforehand that I was entitled to a new Sky box upgrade as my current box isn't Anytime+ compatible. I waited a month for Sky to follow up on that promise but they didn't, so I called their 'Help' line and arranged the insurance/repair.
The Sky engineer replaced the box with a new 1Tb one and that worked - he showed me the fan/ventilation hole on the Thomson box which was clogged with dust, which may have been the cause..
Annoyingly, a day after the engineer's visit, I received a Sky offer in the post saying that I was entitled to a free new HD box... Grrr!...
Very annoyed with Sky (they had promised me a free upgrade but not followed up on it, then belatedly contacting me AFTER I had taken out 'protection' (what a racket!) - due to this shambles of a 'service', I managed to get a small discount on my subscription (20% for next 6 months).
During some of these phone calls to Sky Help, I had also tried to cancel my ESPN subscription but was offered 3 months free ESPN... only for my ESPN to be cancelled completely a couple of days after I had spoken to that Sky 'help' operator!... also followed-up on tha poor service and managed to get them to give me the promised freebie...
Anyway, you might want to try to get a free upgrade from Sky, e.g. if your current Sky box isn't Anytime+ compatible (and if you're also a Sky broadband customer).
END OF STORY/MINI-RANT!