Main site not redirecting properly after install

I installed wpms on my root folder, main domain ( i have several) i checked and everything was fine but after I instllled the multinetwork plugin and added a network i now get this message when i try to access the site:

The page isn’t redirecting properly.

Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

What have I done wrong and how can I fix it?

Thanks!