Fatal error after attempting to install plugin

I recently upgraded to Omeka 1.2.1, which went fine and after the upgrade, everything was working okay. However, after I attempted to install a plugin (I believe it was the Docs Viewer, but it may have been Dublin Core Extended) I now get this error message:

Fatal error: Call to undefined function spl_object_hash() in /var/www/html/omeka/application/libraries/Omeka/Plugin/Loader.php on line 123

Any ideas on how to move past this? Many thanks.

This sounds like a problem with your PHP installation being out of date.

Omeka requires at least PHP version 5.2.4.

Our server did not have PHP 5.2.4 installed - so once I get our IT department to upgrade - I will know in a week or two whether this is the problem. Many thanks for the suggestion!