I've done a few "budget servers" for my own self a few times - all AMD XP motherboards. Anyway, always with Fedora, I've had a really weird problem. All will go just fine with the install, but when I try to run it without any peripherals plugged in (no mouse, keyboard), the server *will not restart*. I plug a keyboard back in, and it works fine.
If I swap the motherboard, it'll work fine. Weird stuff. To me it seems that some motherboards work ok, and some don't. I can't figure out what it is - I just have to switch the mobo brand.
It's not just cheap AMD-based boards that you'll see this on. I've dealt with some fairly expensive Dell servers that do this same crap.
The motherboard expects there to be a keyboard plugged in and the BIOS is probing for it. More advanced BIOS' will simply catch the error and move on.
Depending on the BIOS your mobo is running, you may have a toggle you can flip in order to tell the system to skip keyboard detection (which on stupid BIOS' will probably just disable the port - if you need to get in post boot, you'll need USB).