I have a sign up training calendar that runs on sharepoint 2010, over the weekend i went to install the latest cumulative update http://support.microsoft.com/kb/2817552 and it seems to have broken the signup process. Whenever some goes to sign up for an event they see the following error what can i do to fix this?

Error

The data source control failed to execute the insert command. d8b915be-5355-4d63-97bb-c9cf3aacad75

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Troubleshoot issues with Microsoft SharePoint Foundation.

Correlation ID: d8b915be-5355-4d63-97bb-c9cf3aacad75

the error occurs when someone tries to add an event in the calendar & this issues seems to be across the entire sharepoint 2010 foundation farm. How can i resolve this without rebuilding the farm?