As I read on an Apple News Page, Apple released yesterday a new upadte for its Thunderbold Macs. Mine (MacBook Pro early 2011) was the first MacBook Pro which used the Thunderbold standard, but my internal software update does not show me the update. If I download the update via this page http://support.apple.com/kb/DL1653 and later I try to install it, I get a message like: "Warning, this software is not usable your system!".
I don't understand this. The release note says, that the new update is for all Macs with Thunderbold. The MacBook Pro, early 2011 has this connection.
MacBook Pro (13-inch Early 2011), OS X Mountain Lion (10.8.3)
O.K., problem solved. I had to click the button (in Mac App Store) "Store - Show all software updates". This because I once had to disable the Thunderbold Update 1.1 (or so), because I installed it many times, but nevertheless It reappeared everytime.