update with 404 errors everywhere

Tonight I clicked the “automatic update” notice at the top of my dashboard and confirmed an update of WP to 3.1.2
All of my posts went to 404 errors. I thought it was a plugin issue so I started updating the plugins as well. Then the entire front page went to a test page… and that is where I am now.
The pages seem to be in tact but not the posts.
Is this a plugin issue? should I deactivate all of my plugins and see where the problem is? Did I do something wrong with the update?

I would love some advice!