[racket-dev] string<? error

Has anyone seen an error like this before:

string<?: expects type <string> as 1st argument, given: #f; other
arguments were: "dcdf0433aca16ea2f5db9a003821f56a718d2da5"

I'm using an older version of racket, 5.0.0.6, but I havent seen the
error until recently. I get the error when I run certain files in
drracket. I started getting the error after making some changes to
stepper code (for example stepper/private/reconstruct.rkt) but I dont
think the error is due to any code I modified because I dont use the
string<? function anywhere and because I get the same error when I run
base racket files like racket/private/small-scheme.rkt and
racket/private/cond.rkt.

Also, I ran setup-plt and the error still occurs. Anyone have any
ideas where the error is coming from?