Ah, excellent. I thought that might be the case. I had exactly the same problem quite recently with my Internet connection.
My advice is to phone their technical support people, tell them what's going on and don't take any rubbish from them!
They told me that the signal in my cable may be "weaker" as a result of my router being on another floor to my master phone socket and having 10+ metres of cable would result in a weaker signal, so he told me to move it. I didn't. I just sat there and argued the toss with the tech support man for about an hour because there had been no previous problems.
I know for a fact I put that cable there and it's worked for 3 years and there's nothing that is obstructing/able to damage it and so on and so forth and changing the cable would of course require pulling the carpet up on the stairs (at least in part!)
Funnily enough, about a day later, everything came back and is now as operational as ever.
Don't follow their advice whatever you do!!
It worked for me. They obviously realised they were in the wrong there and just tried to use their on-screen tech support mumbo-jumbo over the phone to me.
Give that a shot and let us know how you get on.
Luke