Because Apple Safari browser has be released 5.1. Some tech point has be changed, Please update your Google Toolbar to the latest version.
Update Google Toolbar.Mac Snow Leopard/Lion: select menu [Safari] - [preference]-[Extensions]
Click Updates, and then click the Install button for the extension you want to update, or click Install All Updates.
To have updatesinstalled automatically whenever they’re available, select Install Updates Automatically.