Seems that there my be an issue with downloaded from the Mac App Store for some people. A thread on the Apple Discussion boards is growing as we speak that tells of some folks woes. Apparently, after installing Xcode for the Mac App Store their hard drives were wiped.
Here are a couple of posts:
“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?” ncsmith4
“No joke this EXACT SAME THING happened to me too!” ncsmith4
At the moment, Apple has not released a fix, so before you install Xcode (or any app for that matter) to be on the safe side you should follow these safety rules:
Update the system. Run Software Update to ensure you have the latest system software and patches on your system.
Run a general maintenance routine. Follow the instructions in this article to clear your system of old temporary files.
Check for hardware problems. Boot to the OS X installation DVD and run a volume verification or fix using Disk Utility. If you have a third-party disk management tool then you can also use this.
Install in Safe Mode. You do not need to run the Xcode installer immediately after downloading it. Instead, boot your system into Safe Mode to disable all but the essential system software components, and install Xcode from there.
Install the package directly. As we mentioned above, when dealing with hanging installations, you might try avoiding the installation application itself and opening the “code and iOS SDK.mpkg” file directly, which will help by avoiding any bugs that may be in the installation wrapper application.