Well, it's a little odd that you get no lights...What Opus is it, 90, 120, 150W? Is it the SFX or the PCB version? What's it mounted on if it's a PCB?
I think I've had a similar problem, and it was related to the cable from the monitor which was in short. What I would suggest is try to pull out all the consumers from the PSU, and run it just with the HDD and the mobo.