This is caused by the system looking for the Eclipse application and not finding it. For the system to locate Eclipse, it needs to be somewhere on the start-up drive. Startup Items are opened before SCSI and networked volumes are mounted. If Eclipse is not on the startup volume, you will receive this message. You will also receive this message if Eclipse is removed from the system altogether and the Eclipse Startup document is still in the Startup folder.
This can also happen on a machine with only one drive. If this happens, try rebuilding the desktop by holding the command and option keys down during startup.