Webmaster Tools Question

Hello how is everyone doing? I have a question that I can not figure out for the life of me. I have a site that was doing well in the search engines and now all of the rankings that were for the home page are gone. the site is not deindexed, and I try to make sure that everything follows Googles guidelines.

The one thing that I did notice is that in webmaster tools there was a 404 error for my main page. This was the page that had the best rankings. The main page is no longer showing in Google at all. I see that there are 10 links that are pointing to the page that are dead. The only thing about this is that when checking the links, they are correct and they are going to the correct page which is pulling up just fine. I did not change anything within the structure of the site, or the permalinks.

Has anyone else run into this before, and is it something that I should be worried about, or something that will correct itself.

Thanks