I say this in the hosting:

"Mucho me temo que nada podemos hacer por nuestra parte, este error se genera cuando joomla no es capaz de generar un error 404 a través de json, y no hay nada a nivel de servidor que nosotros podamos hacer para solventarlo."

"I'm afraid I can do nothing on our part, this error is generated when joomla is not capable of generating a 404 through json, and nothing at the server level that we can do to solve it."

Could you help me?

Thank's

Hello jasonargo ,

I am really sorry for the delay of this reply as it is a weekend for us here.
I remember you have reported this error before right? -> http://stackideas.com/forums/urgent-error-displaying-the-error-page
Which mean that your current PHP 5.3 version also hitting this error right?

Can you do my favour to check which page is usually hitting this error one? So that we can check on this? Please advise.
Basically that error means is just your current template cannot handle those error very well so it show blank page and that error message. After you refresh that it work back normal. We believe that somewhere hitting some php error so that keep hitting this error message in your page.