[racket] Cannot open file in Racket 5.1.2

Whenever I try to open a file in the new version of Racket (on
Windows), I get the following error.  Anyone else having this problem,
or could this be related to the other virus-checking problems I had
with the install?

sequence-contract-violation: negative: method end-edit-sequence cannot
be called, except in states (in-edit-sequence)

 === context ===
C:\Program Files\Racket\collects\framework\private\text.rkt:1511:24
C:\Program Files\Racket\collects\mred\private\wx\common\timer.rkt:34:38
C:\Program Files\Racket\collects\mred\private\wx\common\queue.rkt:430:6
C:\Program Files\Racket\collects\mred\private\wx\common\queue.rkt:470:32
C:\Program Files\Racket\collects\mred\private\wx\common\queue.rkt:607:3