Survey finish error

Hi,

I have a menu that start a public survey.

When i have finished the survey, redirect to the index page of the website but then, appears a many redirect error saying that "Usted ya ha respondido a esta encuesta. Si usted esta leyendo este mensaje de error, contacte con el manager/administrador de la encuesta." (in spanish); "You already responded to this survey. If you are seeing this message in error, please contact survey manager/administrator" (in english).

And when I tried to access to the survey menu, appears another error for redirect problem and if I access to index, I have the same problem.

The web is http://partehartzea.sopelaudala.org, and the survey access is "ENCUESTA 2013"

What´s the problem?, what can I do to solve this?

Note: It´s urgent than the website is for a council.

Thanks