[racket] Unable to use Step in Dr. Racket

Hi,

I am new to scheme. I am trying to run small programs from SICP on Dr. Racket.

This is my code:
(define (factorial n)
  (if (= n 1) 1
      (* n (factorial (- n 1)))))

(factorial 5)

It runs fine. When I click the "Step" Button, I get an error like this:

sequence-contract-violation: negative: method insert cannot be called,
except in states (unlocked), args ")" 408

 === context ===
/usr/local/lib/racket/collects/mred/private/snipfile.rkt:256:6: flush-text
/usr/local/lib/racket/collects/mred/private/snipfile.rkt:279:9
/usr/local/lib/racket/collects/mzlib/private/port.rkt:53:7
/usr/local/lib/racket/collects/racket/pretty.rkt:978:7: pr
/usr/local/lib/racket/collects/racket/pretty.rkt:1210:9: loop
/usr/local/lib/racket/collects/racket/pretty.rkt:978:7: pr
/usr/local/lib/racket/collects/racket/pretty.rkt:1210:9: loop
/usr/local/lib/racket/collects/racket/pretty.rkt:978:7: pr
/usr/local/lib/racket/collects/racket/pretty.rkt:1210:9: loop
/usr/local/lib/racket/collects/racket/pretty.rkt:978:7: pr
/usr/local/lib/racket/collects/racket/pretty.rkt:1210:9: loop
/usr/local/lib/racket/collects/racket/pretty.rkt:978:7: pr
/usr/local/lib/racket/collects/racket/pretty.rkt:1210:9: loop
/usr/local/lib/racket/collects/racket/pretty.rkt:978:7: pr
/usr/local/lib/racket/collects/racket/pretty.rkt:422:3: generic-write
/usr/local/lib/racket/collects/racket/pretty.rkt:234:18
...

Information:
Dr. Racket 5.1.3 using the latest x86_64 installer on Ubuntu 11.04 64
bit, with the "beginning student" language pack.

I tried it on a Windows Machine and it works beautifully. Please let
me know how I can re-install it to work properly on my linux machine.

Thank you,
Anirudh

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