HI Jason, I see you had no responses. I am using Moodle 2.6 and I get the exact error you describe in an Assignment. It also happened quite suddenly. This Assignment used to work but is now broken.
I can however view the assignment and download the results of submitted work, but when I try and edit the assignment, I run into trouble. I cannot even click on the Cancel button successfully without this error showing up.
I get the same error when I duplicate the assignment and try and work with the duplicate.
I hope there is someone out there that can help with this?
(Edited by Mary Cooch -to clarify title original submission Wednesday, 8 October 2014, 11:47 AM)