thanks. Unfortunately I cannot reproduce this on my machine but the thing I would do if I could would be to start putting printfs in to try to find a smaller programs that gets stuck. <div> </div><div>Robby On Sunday, May 4, 2014, Geoffrey S. Knauth <<a href="mailto:geoff@knauth.org">geoff@knauth.org</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> On May 4, 2014, at 16:44 , Robby Findler <<a href="javascript:;" onclick="_e(event, 'cvml', 'robby@eecs.northwestern.edu')">robby@eecs.northwestern.edu</a>> wrote: > That suggests to me that it is running of the of the examples in > /Users/gknauth/test/plt/git/plt/pkgs/racket-pkgs/racket-doc/scribblings/guide/let.scrbl > that's causing the problem. Does this terminate: > $ racket -l scribblings/guide/let.scrbl While I watched two rabbits run in circles in the backyard and observed another rabbit ignore that race condition to bound across the neighbors', no dogs in sight, I let things get good and stuck, then I pressed ^C. Here sir, is your error trace: $ pwd /Users/gknauth/test/plt/git/plt/pkgs/racket-pkgs/racket-doc $ racket -l scribblings/guide/let.scrbl ^Cuser break context...: /Users/gknauth/test/plt/git/plt/pkgs/sandbox-lib/racket/sandbox.rkt:883:2: user-eval /Users/gknauth/test/plt/git/plt/pkgs/scribble-pkgs/scribble-lib/scribble/eval.rkt:399:0: do-plain-eval /Users/gknauth/test/plt/git/plt/pkgs/scribble-pkgs/scribble-lib/scribble/eval.rkt:261:2 /Users/gknauth/test/plt/git/plt/pkgs/scribble-pkgs/scribble-lib/scribble/eval.rkt:550:0: do-titled-interaction /Users/gknauth/test/plt/git/plt/pkgs/racket-pkgs/racket-doc/scribblings/guide/let.scrbl: [running body] </blockquote></div>