Sounds like the machine just hung up on something in Aperture. Honestly, using any intensive programs (pro-apps, parallels/fusion, photoshop) is always going to cause a little trouble.
Happens to me once every few months.. Everything's frozen, music keeps playing. I usually leave it alone for 10 minutes to do its thing, and more often than not it will recover without needing to be unplugged. Your machine is almost certainly not defective.
My iMac is about 1 week old, and it has already frozen 7 times. Perhaps I push it too hard, but my ThinkPad could handle this kind of work with no problem.