My deployment of a rails app with capistrano is failing and I hoping someone can provide me with pointers to troubleshoot. The following is the command output

andrew@melb-web:~/projects/rails/guestbook2$ cap deploy:setup  
  * executing `deploy:setup'  
  * executing "mkdir -p /var/www/dev/guestbook2 /var/www/dev/guestbook2/releases   /var/www/dev/guestbook2/shared /var/www/dev/guestbook2/shared/system    /var/www/dev/guestbook2/shared/log /var/www/dev/guestbook2/shared/pids &&  chmod g+w   /var/www/dev/guestbook2 /var/www/dev/guestbook2/releases /var/www/dev/guestbook2/shared /var/www/dev/guestbook2/shared/system /var/www/dev/guestbook2/shared/log /var/www/dev/guestbook2/shared/pids"
    servers: ["dev.andrewbucknell.com"]
Enter passphrase for /home/andrew/.ssh/id_dsa: 
Enter passphrase for /home/andrew/.ssh/id_dsa: 
    [dev.andrewbucknell.com] executing command
    command finished
andrew@melb-web:~/projects/rails/guestbook2$ cap deploy:check
  * executing `deploy:check'
  * executing "test -d /var/www/dev/guestbook2/releases"
    servers: ["dev.andrewbucknell.com"]
Enter passphrase for /home/andrew/.ssh/id_dsa: 
    [dev.andrewbucknell.com] executing command
    command finished
  * executing "test -w /var/www/dev/guestbook2"
    servers: ["dev.andrewbucknell.com"]
    [dev.andrewbucknell.com] executing command
    command finished
  * executing "test -w /var/www/dev/guestbook2/releases"
    servers: ["dev.andrewbucknell.com"]
    [dev.andrewbucknell.com] executing command
    command finished
  * executing "which git"
    servers: ["dev.andrewbucknell.com"]
    [dev.andrewbucknell.com] executing command
    command finished
  * executing "test -w /var/www/dev/guestbook2/shared"
    servers: ["dev.andrewbucknell.com"]
    [dev.andrewbucknell.com] executing command
    command finished
You appear to have all necessary dependencies installed
andrew@melb-web:~/projects/rails/guestbook2$ cap deploy:migrations
  * executing `deploy:migrations'
  * executing `deploy:update_code'
    updating the cached checkout on all servers
    executing locally: "git ls-remote [email protected]:/home/andrew/git/guestbook2.git master"
Enter passphrase for key '/home/andrew/.ssh/id_dsa': 
  * executing "if [ -d /var/www/dev/guestbook2/shared/cached-copy ]; then cd /var/www/dev/guestbook2/shared/cached-copy && git fetch  origin && git reset  --hard 369c5e04aaf83ad77efbfba0141001ac90915029 && git clean  -d -x -f; else git clone  [email protected]:/home/andrew/git/guestbook2.git /var/www/dev/guestbook2/shared/cached-copy && cd /var/www/dev/guestbook2/shared/cached-copy && git checkout  -b deploy 369c5e04aaf83ad77efbfba0141001ac90915029; fi"
    servers: ["dev.andrewbucknell.com"]
Enter passphrase for /home/andrew/.ssh/id_dsa: 
    [dev.andrewbucknell.com] executing command
 ** [dev.andrewbucknell.com :: err] Permission denied, please try again.
 ** Permission denied, please try again.
 ** Permission denied (publickey,password).
 ** [dev.andrewbucknell.com :: err] fatal: The remote end hung up unexpectedly
 ** [dev.andrewbucknell.com :: out] Initialized empty Git repository in /var/www/dev/guestbook2/shared/cached-copy/.git/
    command finished
failed: "sh -c 'if [ -d /var/www/dev/guestbook2/shared/cached-copy ]; then cd /var/www/dev/guestbook2/shared/cached-copy && git fetch  origin && git reset  --hard 369c5e04aaf83ad77efbfba0141001ac90915029 && git clean  -d -x -f; else git clone  [email protected]:/home/andrew/git/guestbook2.git /var/www/dev/guestbook2/shared/cached-copy && cd /var/www/dev/guestbook2/shared/cached-copy && git checkout  -b deploy 369c5e04aaf83ad77efbfba0141001ac90915029; fi'" on dev.andrewbucknell.com
andrew@melb-web:~/projects/rails/guestbook2$

The following fragment is from cap -d deploy:migrations

Preparing to execute command: "find /var/www/dev/guestbook2/releases/20100305124415/public/images /var/www/dev/guestbook2/releases/20100305124415/public/stylesheets /var/www/dev/guestbook2/releases/20100305124415/public/javascripts -exec touch -t 201003051244.22 {} ';'; true"
Execute ([Yes], No, Abort) ?  |y|  yes
  * executing `deploy:migrate'
  * executing "ls -x /var/www/dev/guestbook2/releases"
Preparing to execute command: "ls -x /var/www/dev/guestbook2/releases"
Execute ([Yes], No, Abort) ?  |y|  yes
/usr/lib/ruby/gems/1.8/gems/capistrano-2.5.17/lib/capistrano/recipes/deploy.rb:55:in `join': can't convert nil into String (TypeError)
    from /usr/lib/ruby/gems/1.8/gems/capistrano-2.5.17/lib/capistrano/recipes/deploy.rb:55:in `load'