Redmine

Hello,
I'm trying to migrate a Mantis 1.2.4 database to Redmine 1.1.1
I use Redmine in windows
I have used the command:

set RAILS_ENV=production
rake redmine:migrate_from_mantis

the result is:

WARNING: Your Redmine data will be deleted during this process.
Are you sure you want to continue ? [y/N] y
rake aborted!
break from proc-closure

(See full trace by running task with --trace)

I try with the --trace option, the result is:

** Invoke redmine:migrate_from_mantis (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute redmine:migrate_from_mantis

WARNING: Your Redmine data will be deleted during this process.
Are you sure you want to continue ? [y/N] y
rake aborted!
break from proc-closure
C:/Inetpub/wwwroot/redmine/lib/tasks/migrate_from_mantis.rake:478:in `call'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `execute'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `each'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `execute'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:in `invoke_with_cal
l_chain'
C:/Ruby187/lib/ruby/1.8/monitor.rb:242:in `synchronize'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_cal
l_chain'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in `invoke'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:in `invoke_task'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `each'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_excep
tion_handling'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:in `run'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_excep
tion_handling'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
C:/Ruby187/lib/ruby/gems/1.8/gems/rake-0.8.7/bin/rake:31
C:/Ruby187/bin/rake:19:in `load'
C:/Ruby187/bin/rake:19

does someone have a solution?