Please read these important notes prior to starting your upgrade.

• Note: If your system prevents your web server from writing to the system temp directory (e.g.,“C:\windows\temp” on Windows or \var\tmp on Linux), upgrading to 4.0.1a may result in a file permissions error. Please visit the Sugar Forums at http://www.sugarcrm.com/forums/showthread.php?p=28613#post28613 to obtain a patch that allows the 4.0.1a upgrade to proceed without error. This patch consists of two PHP files that must be applied before performing the 4.0.1a upgrade. More information about the patch is contained in the above-mentioned forum’s post.
• The Upgrade Wizard is the only supported method for upgrading to Sugar Suite 4.0.1a. The Upgrade Wizard includes critical upgrade logic as well as the SQL commands needed to upgrade to Sugar Suite 4.0.1a.
• Attempting to manually upgrade by simply replacing files and running the upgrade SQL will not work and is not supported. You must use the Upgrade Wizard.
• Backup your system first. It is imperative that you perform a backup of your current Sugar directory and your database before beginning the upgrade process.