Opening WP dashboard

I am using FF, Chrome and IE8 and I am trying to open my Wordpress dashboard and I am constantly getting Page not found. I’ve been refreshing over and over and it is not coming up (we’re talking, so far, about 20 minutes). This actually happens quite a lot but today it is especially slow. I have the most updated WP and very few plugins.

I don’t understand why this is always so slow.[hr]
I am also getting Error 404 - File Not Found for the page I am trying to open. In 1 hour I had it open once in one of the browsers but when I saved, I am back to the not opening run-around.

Also getting 505 Internal Server Error…this is getting ridiculous.