Install Xcode from the App Store = Deleted System
Last night, I bought the $4.99 Xcode app from the App Store. Once it was done downloading, I told it to go ahead and install, and... about halfway through it's install I noticed my applications were deleting one by one. Frantically, I shut my system down with a hard shut down. Upon reboot, sure enough, the HD wouldn't reboot.
I reinstalled my system from a Time Machine backup, still wouldn't boot, but I overcame the booting issue by reinstalling OSX over the restored drive.
Once I got everything back up and running, I thought to myself "surely, an App Store download of Xcode couldn't cause such irradic behavior" so with a morbid curiosity (and knowledge that i can restore if need be) I gave it another shot... and sure enough: just like before, about halfway through the Xcode install, my apps and system library files started disappearing. Less panic'd I stayed around as long as I could before doing the hard shut down. Leaving Safari open saw it slowly loose necessary files to run (fonts, images, etc) not that the app itself was around anything anymore anyway.
Truly odd behavior, and it'll keep me from installing Xcode unless there's a real solution to the problem out there. So I put it to you, Apple faithful and forum moderators... thoughts?
Mac Pro (early 2009), Mac OS X (10.6.6)