Problem solved.
As for the other guys, it was a problem from the USB flash drive.
I could not believe it, because it was running perfectly the first 3 times I did the install.
I am running from another USB drive with UniBeast and all is good.
I checked the 1st USB drive and it's dead. Can't format, can't mount on OS X (or Windows XP)
First time in 10 years that a USB drive dies on me.
I hope it was just bad luck and bad coincidence. (really hope it was nothing from the new motherboard that killed this USB drive.)
Let see in the future.
So, if you get "boot1: error", find a new USB drive to try UniBeast. As simple as that !