[Marcos Ganan]

In my case, that error comes when you have 2 outputs of the same project witch. I was open a project made in CS5 into the new CS5.5. That reports this error. Another once, I tried to render one project through Media Encoder which crashed for some reason, and then, from AE I could not do it, because of the same error. Clean your disk cache and reset preferences (Cmd+Alt+Shift while start the software) and delete posible projects with the same output in the render queu.