Redmine

I am running redmine trunk r2835, with ruby 1.8.7 and rails 2.2.2.
When I try to receive mails from our IMAP Server at Strato.de , I get the following exception.
Don't know what other information you need, if there is anything I can help you with, please let me know.

# rake -f /var/www/redmine/Rakefile redmine:email:receive_imap RAILS_ENV="production" host=imap.strato.de ssl=true \
    port=993 username=binoli@redmine.domain.de password=******** project=binoli \
    move_on_success=redmine-success move_on_failure=redmine-failure --trace
(in /root)
** Invoke redmine:email:receive_imap (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute redmine:email:receive_imap
rake aborted!
undefined method `[]' for nil:NilClass
/usr/lib/ruby/1.8/net/imap.rb:1160:in `search_internal'
/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/usr/lib/ruby/1.8/net/imap.rb:1154:in `search_internal'
/usr/lib/ruby/1.8/net/imap.rb:679:in `search'
/var/www/redmine/lib/redmine/imap.rb:32:in `check'
/var/www/redmine/lib/tasks/email.rake:127
/usr/lib/ruby/1.8/rake.rb:617:in `call'
/usr/lib/ruby/1.8/rake.rb:617:in `execute'
/usr/lib/ruby/1.8/rake.rb:612:in `each'
/usr/lib/ruby/1.8/rake.rb:612:in `execute'
/usr/lib/ruby/1.8/rake.rb:578:in `invoke_with_call_chain'
/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/usr/lib/ruby/1.8/rake.rb:571:in `invoke_with_call_chain'
/usr/lib/ruby/1.8/rake.rb:564:in `invoke'
/usr/lib/ruby/1.8/rake.rb:2027:in `invoke_task'
/usr/lib/ruby/1.8/rake.rb:2005:in `top_level'
/usr/lib/ruby/1.8/rake.rb:2005:in `each'
/usr/lib/ruby/1.8/rake.rb:2005:in `top_level'
/usr/lib/ruby/1.8/rake.rb:2044:in `standard_exception_handling'
/usr/lib/ruby/1.8/rake.rb:1999:in `top_level'
/usr/lib/ruby/1.8/rake.rb:1977:in `run'
/usr/lib/ruby/1.8/rake.rb:2044:in `standard_exception_handling'
/usr/lib/ruby/1.8/rake.rb:1974:in `run'
/usr/bin/rake:28