How do I repair fatal errors from NextGen Gallery

Recently I updated an older version of wordpress to WP 3.1.4 because wordpress was complaining that NextGen Gallery is no longer supported on the older versions of wordpress so I did a backup and updated wordpress manually. The site comes up fine and doesn’t look broken any more but now can’t log into the admin section.

I get the following error:

Warning: require_once(/var/www/vhosts/cortneyhelaineevents.com/httpdocs/wp-content/plugins/nextgen-gallery/admin/admin.php) [function.require-once]: failed to open stream: No such file or directory in /var/www/vhosts/cortneyhelaineevents.com/httpdocs/wp-content/plugins/nextgen-gallery/nggallery.php on line 316

Fatal error: require_once() [function.require]: Failed opening required ‘/var/www/vhosts/cortneyhelaineevents.com/httpdocs/wp-content/plugins/nextgen-gallery/admin/admin.php’ (include_path=’.:’) in /var/www/vhosts/cortneyhelaineevents.com/httpdocs/wp-content/plugins/nextgen-gallery/nggallery.php on line 316

I think this is a problem with NextGen Gallery plugin, but not if any one could help with this it would be much appreciated.

Thanks in advance