Like the thread about Djokovic, I think Murray needs a thread like that.
Here's what I think.
I think Murray has lost his bravery/courage.
He's really worked a lot in last two years : working physically, practising a lot, and playing with the aim of a game with "zero error".
This was a lot of work
And yet he didn't achieve anything he wanted, at slams I mean, of course.
Then I think he's lost his bravery/courage, not able to give everything as he was in the beginning of 2009.
I think that's the main problem.
It reminds me of what many people have said about Nadal : worked a lot, yet stayed number 2, which might have made him lose his courage.
But first Nadal's mentality is of course different (he has a very solid and strong "fighting background" imo) and secondly, at least Nadal had one slam to win every year, in Roland-Garros.
Even Nadal had some moments of losing bravery (for instance when he cried after Wimbledon final in 2007), but he had Roland-Garros. And also he had the fact that he beat the number 1 more often than the number 1 beat him. That gives courage.
Of course some might also compare with Djokovic in the middle of 2008 losing courage after being beaten by Nadal several times, but Djokovic's current situation is imo much more complicated to understand.
I don't think Murray is as "brave" as Nadal, and he's lost some courage here.
Lightening his schedule without maybe any major justification other than some laziness, being less concentrated, making sometimes quite silly things ... it's like that.
Many speak about changing team (ie Todd Martin) for Djokovic but that may also be a good idea for Murray, as I think that in the long term, Murray needs to change his game to attack more, and it may be the right moment : now that he's lost bravery, it's not a good situation to keep on grinding again and again. He might do it on clay next months, but if he's lost bravery what can he win on clay like that ? Maybe he might skip Monte-Carlo and rather prepare for Wimbledon, practising a more attacking game.
I have the impression that McLagan has never encouraged him to play someway else.
I think he has to change something, both for his game and for his mental.