All regions of channel 4 are on a 2A North transponder, which is an odd one to loose in the UK, normally the south beam ones would be affected first by a poorly aligned dish. Unless it is interference from something nearby causing it.
Sci-Fi UK,
Sky Sports News,
Sky Sports 1 Ireland, British Eurosport 2, Hallmark Channel UK,
Sky Sports Xtra, Discovery Real Time +1 are on a nearby transponder, are they affected?
As for the dreambox, if you search/post in the drambox section here I'm sure people will be able to help.