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It wouldn’t be the first time an update of a plugin or theme creates problems.
Have you tried this yet:

1. Use FTP to access your site
   e.g. http://filezilla-project.org/download.php
2. rename all plugins by putting a ‘0’ in front of each plugin -folder;
   ../wp-content/plugins
3. Check if the access / ‘normal functioning’ has been restored
4. If so: one-by-one, remove the ‘0’, checking every time to see if the problem re-occurs.
5. when the problem re-occurs, you’ve found the source of the problem; Delete and find a similar plugin that works with your site
6. alternatively: FTP:Delete; Then download and install / activate a NEW version of the problematic plugin and see if this works.

Alternatively:
Instead of ftp, use the webaccess dashboard functions provided by the webhost.
This usually is not as versatile and more cumbersome.