[Conkeror] Cannot follow link number 13 on a site

[Tassilo Horn]

Hi all,

On http://pi.informatik.uni-siegen.de/Projekte/sidiff/index.php I cannot
follow the link no 13 or better, I can't even enter it.  I enter 1 and
the minibuffer shows

    Follow(select link): #1_

where _ is "point".  When I hit 3 then, I get

    Follow(select link): #3_

Somehow my 1 is gone...

The links 12 and 14 work, though.  Is it because 13 means disaster?
Does conkeror try to save me? ;-)

Bye,
Tassilo