psu problem? hELP

[cjm18]

I have an Antec 400w psu w/ 18a on the 12v rail.
just went from a 6800nu to a 7800 gt.

problem= i plug in the power cord to the back and the fans and mobo light turns on. no boot no video nothing else
I press case power and nothing happens.
Is this a short or a bad psu?

 

[pilotace001]

are jumpers on the correct settings / power wire > mobo ?
thats all I can suggest as far a psu knowledge...