Internal error installing Mac OS X 10.6 core library

this is on a clean 1-month old mac running 10.6.7, with a fresh install of Xcode 4 from the app store. The "documentation" tab in the options allow you to install the mac os 10.6 core library documentation. It downloads the package but fails to install it. Here's the error: "Internal error installing Mac OS X 10.6 Core Library". Install process rejected install attempt.

开发者_如何学编程What can be done to fix this? Thanks.

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step 1 : Exit XCode And Remove Old Mac OS X 10.6 Core Library.
Default Position :
/Library/Developer/Documentation/DocSets
File Name :
com.apple.adc.documentation.AppleSnowLeopard.CoreReference.docset

step 2 : Download Again.
Open XCode And Select Menu XCode / Preferences... / Documentation, 
get Mac OS X 10.6 Core Library(661 MB) Again.
ps : In Fact, file size is 1.31 GB, Not 661 MB

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I have solved it by downloading the documentation manually from:

http://developer.apple.com/rss/com.apple.adc.documentation.AppleSnowLeopard.atom

Apple servers are overloaded, and the download process may end up blocked several times. To address it, I executed a progressive download with the "-C -" option, i.e.:

$ curl -C - -O http://devimages.apple.com/docsets/20110309/com.apple.adc.documentation.AppleLegacy.CoreReference.xar

After that, it is necessary to uncompress and change the permissions using:

$ xar -x -f com.apple.adc.documentation.AppleLegacy.CoreReference.xar
$ sudo chown -R -P _devdocs /Library/Developer/Documentation/DocSets/com.apple.adc.documentation.AppleLegacy.CoreReference.docset