Only Main page shows as "Not found"

Hi there,
My main page shows “Not found”, with any theme, already tried to set permalinks to default, no luck.
https://diegoalgara.com/
Not found, but a test post does work:
https://diegoalgara.com/2010/10/02/prueba/

Any help?

I’m coming from WP MU, did a migration to WP 3, the updated to WP 3.0.1 and my main site had a redirection loop.
Fixed it placing the example code for .htaccess from the bottom of:
https://codex.www.ads-software.com/Create_A_Network
Subdomain, as I already had that install mode with mu domain mapping.
And placing manually the code for Network and Multisite, at wp-config.php, like so:
define(‘WP_ALLOW_MULTISITE’, true);
define(‘SUBDOMAIN_INSTALL’, yes);