[racket] Sandbox needs to access preferences? Why?

Hi all,

I'm trying to write a checker script for the handin server (which is running on my Mac), and when i try handing an assignment in to it, I am getting the error that read access to my preferences file is denied:

  ERROR: file-or-directory-modify-seconds: 'read' access denied for
    /Users/myusername/Library/Preferences/org.racket-lang.prefs.rktd

In the checker I am creating two evaluators, one using make-evaluator/submission and the other using make-module-evaluator.  I have determined that this definition is provoking the error:
;;
(define-values (asg-eval solution-eval)
          (parameterize ([sandbox-namespace-specs
                           (list make-base-namespace 'hw/solutions)])
            (values
             (make-evaluator/submission
              '(special intermediate)
              '()
              submission)
             (make-module-evaluator (build-path asg-dir "solution.rkt")))))
;;

submission is bound by the handin server's check: macro, and asg-dir is defined thus:
(define asg-dir (build-path server-dir "my-handin-directory-here"))
where server-dir is also provided by the handin server.  solution.rkt is a file I have written in ISL, which depends only on 2htdp/image and a library I've linked as hw/solutions.

Can you identify what may be triggering the attempt to read preferences, and how I can either avoid it or grant appropriate read permissions?  Thanks...

Best,
Jordan