Error in pagin navigation

Hi everybody:

I’ve installed WordPress 3.0 in my server with “obscure” template. The url is https://www.enfocax.org

Later I installed the PageNavi for make the pagin in my blog but if you clik in the second page the URL that I obtain is https://www.enfocax.org/index.php/Index.php/page/2/ , but this page is in blank. The correct URL that I must obtain is https://www.enfocax.org/index.php/page/2/

Why it?

I’ve tried to reinstall the plugin and I’ve tried to instal other (WP Digg Style) but I obtain the same erroneus URL. For this reason I suppose that this error is really in my WordPress configuration

I looking for in differents forums and websites but I’ve not found answer ?Anybody can help me?

Many thanks and sorry for my English

Juan Antonio