Updated a plugin and now my blog posts are missing?

First thing to try is deactivating the Contact Form plugin just long enough to see if your blog posts re-appear.

If that doesn’t fix it, please provide a link (URL) to your site, so we can take a look.

On the Admin screen on your site that is shown here:
http://codex.wordpress.org/Settings_Permalinks_Screen
please try clicking the Save Changes button without making any changes.

If things don’t work after that, please check that .htaccess exists in the /blog/ folder on your web site.

You didn’t mention if things worked after deactivating the Contact Form plugin.