Xcode 4.1 comes with a nice tool called Network Link Conditioner, which is basically a GUI to configure certain settings of your network to make it behave like a "Lossy Edge Connection" or something similar. Why would anyone want to do this? In a nutshell, a bunch of bugs in iOS apps are only visible in such environments and hard to catch in office settings with perfect connections. So, to work around that perfect connection, this tool has been invented
Apple-like, it looks great and ... doesn't work ( which is not that Apple-like at all ). At least on my brand-new Early 2011 MBP, it just crashes. So I got curious and ask some friends to double-check it, and bingo, they had similar issues on the comparable i7-equipped machines.
Back at home, I fired the tool on my ancient 2009 iMac, and voila, it works just fine. So.. what the hell is going on there?
[update] I tested the network link conditioner on my new i5-iMac, not a problem there.
[update] It seems Nick Pannuto found a solution for the problem, which you can find filed under the Apple Radar with the id 11013262. Thanks!