Not sure if anyone else has noticed this, but thought I'd report it here.
I downloaded the QT 4.7 version for VS2008, along with the VS plugin. After QT installed (without errors), it ran the "Examples and Demos" program. After messing around viewing a few different demos, it locked hard - no mouse movement, no alt+ctrl+delete, etc.. Had to power down.
I tried this on another machine, totally different hardware, but also running Windows XP Pro. Same thing - seems to randomly lock up, and when it locks, it locks hard.