I have a US v7 with Messiah 2 and it boots using AR2 (same product).
There is another thread on another forum with a similar problem (won't boot from browser). In that case i thought it might be a voltage problem.
Has the pcb track been cut as per advice given in my install guide on
www.messiah2.com? This would assure the correct voltage to the Actel chip on Messiah 2.