ML clean install from USB stick not working

hello,

i'm trying clean install mountain lion same way did lion (extracting installesd.dmg, putting on usb stick).
unfortunatley imac 27" 2010 won't boot it. stays looping little progress wheel.

got solution this?

 

is usb flash memory thumb drive formatted?

how format new hdd/ssd install mac os x or make bootable copy onto​

did take similar steps shown in guide?
make os x lion boot disc

 

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