"Received an invalid response from the server" and languages

Hi, i had the same problem of this thread http://drupal.org/node/538022.

In my case i have a spanish site. I saw in the watchdog a message like this:
"page not found 23/12/2009 - 12:35 es/hierarchical_select_json"

Note that the problem is the language path prefix. I solved the problem deleting the path prefix for the spanish language. (and for english, i put 'en' prefix)

I think this is a problem for multilingual sites.