Motherboard problem - Front USBs working but back USBs not working

[Mastermage]

I recently experienced problem with my power button. It stopped working . I exchanged the wires of power and reset button and now I am using reset button as power button. This worked fine but when I switched on my PC, I noticed that USB port at the back are not working properly but front ones are working properly. Also audio input ports at the front and back both are also not working.

I browsed many posts and tried all of that.

I uninstalled all usb device drivers and installled them again.
Installed latest device drivers from updates.
Even clean installed windows 7.
But nothing happend.

I also removed all the wires attached to motherboard, cleaned the motherboard, checked all the wires, but, no help.

My motherboard is Gigabyte G41MT-S2P

 

[chugot9218]

Are the standoffs all in properly? Is this a new build?

 

[Mastermage]

Are the standoffs all in properly? Is this a new build?

Thanks for the reply.

No, it's is not a new build.
I don't know what are 'standoffs'?