This has me completely stumped......
I have two identical motherboard, identical BIOS, identical CPU and one can boot ESXi and the other hangs at "loading module USB". These were both running ESXi 4.0 update 1 and now I can't get the second one past the hang.....well I can, I stumbled upon it when pressing the power switch, each time I press the power switch ESXi would go on to the next module and after about 6 or so presses it would eventually boot and it seems to work. On the console there are messages to the effect that the processor halted for X number of ms. Thinking that my CPU or mobo was stuffed, I replaced it with another similar CPU mobo and yet the messages are still appearing. Now I don't believe in coincidence and the fact that my tests would suggest both CPU/Mobo combinations are broken makes me suspicious. I have tested the RAM with memtest (100% OK) and I even ran windows 7 on the box with a copy of Prime running flat stick (Quad core) overnight and it was fine also.
I am at a loss and would really appreciate some help.