I don't think that it is a great surprise that some Lib Dems feel uncomfortable with some of the policies that they have had to vote for as part of the Coalition in the same way that members of the same party are not going to agree on all matters but Vince Cable and some of his colleagues have certainly been naive in letting journalists from the Telegraph pose as constituents and speaking too candidly too them.
http://www.bbc.co.uk/news/uk-politics-12053656
http://www.telegraph.co.uk/news/newstopics/politics/liberaldemocrats/8218224/Liberal-Democrat-ministers-condemn-scrapping-of-child-benefit.html

If I were slightly more cynical I might detect underhand tactics other than those of the Telegraph reporters as Cable has been stitched up to the extent that his public rebuke and stripping him of the Murdoch decision humiliates him enough to keep in line whilst hanging onto his job, without actually sacking him where he may become a more ferocious critic on Coalition policy from the back benches. The old adage of better having your enemies inside the tent pissing out rather than outside the tent pissing in rings true here and also allows a Tory friendly to Murdoch in Jeremy Hunt to take the leading role in News Corporations proposed takeover of BSkyB. Cables attitude towards Murdoch will hardly have come as a major shock to Cameron and Osborne so this provides them with the perfect opportunity of putting someone more pro Murdoch in his place - although if he is as pro Murdoch as some of his comments suggest doesn't that make him as impartial as Cable.

But would it matter if Rupert Murdoch owned two TV news channels in Britain? "The important thing is not whether a particular owner owns another TV channel but to make sure you have a variety of owners with a variety of TV channels so that no one owner has a dominant position both commercially and politically.
"Rather than worry about Rupert Murdoch owning another TV channel, what we should recognise is that he has probably done more to create variety and choice in British TV than any other single person because of his huge investment in setting up Sky TV which, at one point, was losing several million pounds a day.
"We would be the poorer and wouldn't be saying that British TV is the envy of the world if it hadn't been for him being prepared to take that commercial risk. We need to encourage that kind of investment."

The above quote is from http://www.jeremyhunt.org/newsshow.aspx?ref=452
Vince Cable has therefore shot himself in the foot and he has ended up with the opposite effect of what he intended. If he was serious about wanting to stop Murdoch becoming all powerful then he should resign his position and criticise freely from the backbenches, a move that would also go somewhere to restoring his credibility.