Important Update
The strange bug is fixed (at least for me) in Xcode 4.2!
I\'ve a serious problem with Xcode 4.1 Build 4B110 under Mac
I've found that if I leave two Instruments windows open at the same time, when Instruments locks up in one window, bringing the other window into the foreground seems to snap Instruments out of it. It seems to bring Instruments back if you can get the focus on a different Instruments window than the one that's locked.
I've found the two-window-method works all the time while the Xcode-profile-method only works sometimes.
Edit:
After trying the two-window-method a bit more, this method also only works sometimes.