server internal error

Dear w3c,
i've got a serious trouble with validator and my hosting.
I registered a new site on joomlabay.it (hostingbay.it) with domain www.studiocattaneo.biz

Well, validator.w3c.org can't get the pages of my website, returning this message error:

500 Internal Server Error
> The server encountered an internal error or
> misconfiguration and was unable to complete your request.
> Please contact the server administrator, [no address
> given] and inform them of the time the error occurred, and
> anything you might have done that may have caused the
> error. More information about this error may be available
> in the server error log. Apache/2.2.9 (Debian)
> mod_python/3.3.1 Python/2.5.2 Server at validator.w3.org
> Port 80

I contact the hosting staff, but they give no answer...
Is there  a configuration by htaccess, or other stuff, that i can do?
I'm very dramatically idle and i can't go on...
Ah!: if I upload my site validate by upload, it works...

Please, give me a chance to make it works!!
Thanks.
Daniele Marsero.