One of our customers had a problem with Platespin backing up a machine to their DR VMware server. It turns out that ESX (starting in 3.5, but can include previous builds because of security patches) has a configuration file that can prevent virtual machines from booting if there is something in the virtual floppy or CD-ROM drive. The fix is to edit the configuration files, using SSH to connect to the ESX console and edit the configuration files with vi. [more]
http://support.platespin.com/kb2/article.aspx?id=21110&query=ESX3TaskFailed