I have an agent that when trying to logon to the CAD application she receives the message, "The Cisco Agent Desktop software update failed." To my knowledge, she is the only agent receiving this message.
Every time you start Agent Desktop, it checks to see if there is an updated version available, or if there was a system configuration change that requires a Windows registry change. If there is, it automatically runs the update process.
For more details about the requirements,refer to the Cisco Agent Desktop User Guide(Pg:6)