If you receive a Mac App Store error message "An error has occurred" while trying to download Mac OS X Lion developer preview, please complete the following:\t1. Ensure you have at least 8GB of disk space available in your home folder. \t\t2. Open ~/Library/Application Support/AppStore/manifest.plist in Xcode. \t\t3. Locate the entry for Mac OS X Lion developer preview and change the value for 'failed' to NO, and 'paused' to YES [in Property List Editor].\t \t4. Move the folder at ~/Library/Application Support/AppStore/420410606 to the Trash. \t\t\t5. Relaunch Mac App Store, navigate to the Purchases tab, and click Resume to begin your download again.