Index Page Disappeared From Serps

Hi,

I have a 2 years old website, today the index page’s rankings have disappeared completely and I lost all of my rankings for that page. The internal pages still have rankings. The index page still has cache and PR and none of the pages in my site seem to have been deindexed.

I haven’t touched my site in a while.

I have experienced that a year ago with a client that suddenly lost his rankings for the index page and then appeared after 3 months. However I have heard a couple of colleagues saying that they have experienced similar problems with some of their websites.

Is this because a google update? or its a temporary problem caused by god knows what?

Please advice

Best,
Carlos.