Computer blocked because of error smpboot CPU2: Not responding

[Paul Smith]

On Fri, Jul 12, 2013 at 6:49 PM, Paul Smith <phhs80 at gmail.com> wrote:
> I am experiencing the following problem while booting Fedora 19:
>
> smpboot: CPU2: Not responding.
>
> The computer seems to be blocked. Is there some way of rebooting it
> without having to power off the computer?

I believe that the cause of this problem was the fact that I had an
external disk connected to the computer. I have meanwhile unplugged
it, but the booting process is totally blocked and I do not know how
to resume it.

Paul