LSO WBT Course Cancellation Workflow Error?

Hi Friends,

I am using the workflow WS12000004 for course cancellation in LSO. This workflow works fine for Class Room training but when i am executing the cancellation of Web based training(WBT) the approver receive the workflow in his business workplace and when clicks to open it it generate the error. The error is shown in the attached image.

Please provide the solution.

Regards

Ramji Dubey