Upgrade from xs7 to xs7.1 fails on poweredge pe 2950

Tring to upgrade a 2 node pool composed by two identical poweredge 2950 nodes.
As soon as the 7.1 installer start from cd and let me choose keyboard layout I receive the
attached error message.

Note i've used the same cd ( media+usb cd drive) to upgrade a pair of hp microserver without any problems.