I didn't watch it myself (preferring to spend my Saturday evening watching Indiana Jones) but there are reports on various forums, both cable and satellite, that the BBC made a right mess of broadcasting the Eurovision song contest in high definition. Digital Spy thread here. 5.1 sound was the initial problem, but there's speculation that the whole HD feed was knackered and ended up with standard definition being upscaled on BBC HD.
Given that this was the first big BBC HD broadcast for the fledgling Freesat service, there's probably plenty of red faces and head-rolling sounds over White City way. Whether the problem was with the BBC or with the services provided by the Serbian hosts, this was embarrassing.
Hopefully, they'll sort it out for the England game on Wednesday. Oh, hang on...they're not broadcasting that in HD...(cue gnashing of teeth)