Good thinking. Looking at the dumps, it appears every case has the ` character. If i run the sproc statements in SSMS it doesn't trigger the exception though. So, I'm not quite sure that it's purely that character doing it...

This is grasping at straws, grrr. I would totally rewrite this sproc, but it's 3000 lines long, and full of crazy business logic I don't understand 🙂