Could be, though i had this problem for about 5 years but that's besides the point..
How is your land line connected? To a BT-style box on the wall or into the back of your Router? Either way, if the service is down and these days your phone is also supplied via the co-ax feed, this will also most likely stop your land line working! Engineers may already be on their way to a defective piece of hardware/cabinet..
You have managed to post here so i assume your Broadband is working, unless you used your mobile? Is your TiVo box working too? Is there another handset or phone in the house that could be faulty or has been left off the hook?
Kind regards,
Lee