Function 'Evaluate' must return a 'Data type not found'. (33

I'm trying to run the exact code that's found in the documentation under the Evaluate command.
I'm getting back an error that says:
Function 'Evaluate' must return a 'Data type not found'. (3334)
Any ideas what could be causing that?
Thanks!
-- James
I'm getting back an error that says:
Function 'Evaluate' must return a 'Data type not found'. (3334)
Any ideas what could be causing that?
Thanks!
-- James