It seems that US broadcasters don't think that the population would be interested in the final episode of the spectacular Frozen Planet series:

New Statesman - US will not air climate change episode of Frozen Planet (http://www.newstatesman.com/blogs/star-spangled-staggers/2011/11/episode-climate-series-bbc)

Not sure that Discovery's "scheduling issue" will convince many people that there isn't an agenda here, even in the US where climate change seems to not be happening.
I'd put money on some helpful person getting a copy of tonight's UK broadcast online for those who don't have a (convenient) "scheduling issue".

Steve

p.s. It seems that Discovery have (sort of) relented and agreed to show it in March, presumably when the furore in those countries allowed to see it this year has died down:

http://www.ecorazzi.com/