Some of them seem to have twigged the Kontiki issue and have dumped the install. However, the problem is all with Sky. These viewers can watch iPlayer and ITV.com with no problems and speed test show they have a reliable connection to the internet. In my view Sky simply aren't provisioning their service properly and need to totally drop P2P and work with a proper CDN.
More savvy users are blaming Sky'd Xbox service: http://www.digitalspy.com/forums/showthread.php?p=37053444. But the issue is the same: if Sky are asking for sky high subscriptions they should be provisioning the service properly.
Also, the use of the pisspoor Silverlight technology, which has been dropped by most serious webcasters (including most recently ITV) exacerbates the problem.
Sky need to sack their tech team, adopt H.264 and a decent VMS and go and speak to the CDN guys as fast as possible. They should also find some people who can redesign their dreadful player whilst they're at it.
Otherwise a reputation they built so well in TV1.0 land will come crashing down around them in the world of internet TV.