Have you recently changed to sky and gotten a nice shiney new router, one which looks like this:
Well, I hope you are enjoying it...
chances are, if you look at it now, it has been rebooted, sorry about that!
Note: I have done absolutely no research into this, so it is all guesses and speculation here are probably wrong.
What was also interesting was an AJAX GET request to "http://192.168.0.1/sky_self_heal_reboot.cgi". It didn't look like there was any verification. Sure enough when the address was put straight into my address bar, the router would reboot.
Fast forward to today, I tried including an AJAX GET request to that page from this page, but that sort of thing is blocked for security reasons. However iframes seem to be happy enough to load a local resource, and hey presto the router rebooted. Awkard.
Update:Ok, Ok, Ok I have removed the actual iframe and just included it as text now so you wont be booted off, it was getting rather anoying, I admit.
On a more serous note...
There has been a bit of traffic from people looking for help with the "Sky Home Hub Self Help" screens. All I can advise, if you are seeing that screen, is that you follow all the steps. Check that all the connections are tight, if you have some spare or old ADSL filters, give them a shot. If you still are not getting connected, chances are that you will need to call Sky and get them out to fix your line, sorry!