[racket-dev] Weird failure w/ DrRacket

Recently, I've been seeing the following behavior:

- Open DrRacket on a file
- add a syntax error
- get this internal error:

vector-ref: contract violation
  expected: vector?
  given: '#s(exn-info "post.rkt:8:0: define: bad syntax in: (define)"
(#(177 9)) () #f)
  argument position: 1st
  other arguments...:
   1

- the definitions window goes blank, and never comes back (for that tab).

Disabling online compilation seems to make the problem go away.

I assume I've done something to break my installation, but I'm not sure what.

Sam