I watched this too. There was nothing 'spoilt' about Serena's behaviour. It stemmed from other things...
If any of you know, there has been 'history' between Clijsters and the Williams girls for a number of years. I would say 'hate' is quite an acceptable description, in fact. If I remember correctly, Kim Clijsters mentioned about disliking the sisters and it all boiled over from there.
This morning game was about anger. Serena towards Kim C, I believe, for having the audacity of beating Venus. I think her hate got on the way of her game and she had to calm herself down on several occasions. I can't quite remember ever seeing Serena smash her racket, like that and that confirmed it to me.
In a way, I feel Serena's outburst was misdirected and also served as a get out clause. I loath saying it as I'm a huge fan, but I say it as I see it. Serena couldn't face serving out on a loss.
I'm hugely disappointed in her, but I know Clijster's return will re-invigorate her to be World Number one as she faces a new challenger.