Error Installing Xcode 4.0.2 and iOS SDK 4.3 - "The Installation Failed"

Trying to install but we dont' get far before it says "The Installation Failed. The Installer encountered an error that caused the installation to fail. Contact the software manufacturer for assistance".

We are using Snow Leopard.

In our console, it says "The Domain/Default pair of (com.apple.iPhoneSDKInstaller, showAdvancedInstaller) does not exist"

We uninstal开发者_开发问答led an older version of xcode completely, and are at a loss as to why this is happening.

I had the same problem with iOS 5 beta just now. Rebooting fixed it.