On IBM x3650 servers,WinPE 2.1 Automation boot hangs at 100% loaded.
Boot to F1 BIOS setup and navigate to CPU options as follows:
Execute Disable Bit is a hardware-based security feature that can reduce exposure to viruses and malicious-code attacks and prevent harmful software from executing and propagating on the server or network.
WinPE 2.1 x86 (x64 bit does not seem to have this issue)
IBM x3650 and possibly x3550