T3600 status lights issue

Hi All,

we have a T3600 with an odd error.

• the power LED is off, but the machine is connected to the mains.
• all 4 LED status lights are on.
• hard drive LED is on solid.

if i disconnect the mains the lights go out of course. 

The PC powers up normally when the power button is pressed.

any ideas what is causing this?

thanks

Jim