Redmine

Hi,
I always get this error during import wiki pages from trac project:

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Trac directory []: /other/trac/myproject
Trac database adapter (sqlite, sqlite3, mysql, postgresql) [sqlite]: sqlite3
Trac database encoding [UTF-8]:
Target project identifier []: myproject

Migrating components.......
Migrating milestones..
Migrating custom fields....
Migrating tickets............................................
Migrating wiki..........................................................................rake aborted!
can't convert nil into an exact number
/usr/lib/ruby/gems/1.9.1/gems/activesupport-2.3.14/lib/active_support/core_ext/time/calculations.rb:286:in `-'
/usr/lib/ruby/gems/1.9.1/gems/activesupport-2.3.14/lib/active_support/core_ext/time/calculations.rb:286:in `minus_with_duration'
/usr/lib/ruby/gems/1.9.1/gems/activesupport-2.3.14/lib/active_support/core_ext/time/calculations.rb:295:in `minus_with_coercion'
/other/apache/htdocs/redmine-1.4.0/lib/tasks/migrate_from_trac.rake:79:in `fake'
/other/apache/htdocs/redmine-1.4.0/lib/tasks/migrate_from_trac.rake:582:in `block in migrate'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-2.3.14/lib/active_record/associations/association_collection.rb:392:in `block in method_missing'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-2.3.14/lib/active_record/associations/association_proxy.rb:215:in `each'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-2.3.14/lib/active_record/associations/association_proxy.rb:215:in `method_missing'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-2.3.14/lib/active_record/associations/association_collection.rb:392:in `method_missing'
/other/apache/htdocs/redmine-1.4.0/lib/tasks/migrate_from_trac.rake:580:in `migrate'
/other/apache/htdocs/redmine-1.4.0/lib/tasks/migrate_from_trac.rake:765:in `block (2 levels) in <top (required)>'
/usr/lib/ruby/1.9.1/rake/task.rb:205:in `call'
/usr/lib/ruby/1.9.1/rake/task.rb:205:in `block in execute'
/usr/lib/ruby/1.9.1/rake/task.rb:200:in `each'
/usr/lib/ruby/1.9.1/rake/task.rb:200:in `execute'
/usr/lib/ruby/1.9.1/rake/task.rb:158:in `block in invoke_with_call_chain'
/usr/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
/usr/lib/ruby/1.9.1/rake/task.rb:151:in `invoke_with_call_chain'
/usr/lib/ruby/1.9.1/rake/task.rb:144:in `invoke'
/usr/lib/ruby/1.9.1/rake/application.rb:116:in `invoke_task'
/usr/lib/ruby/1.9.1/rake/application.rb:94:in `block (2 levels) in top_level'
/usr/lib/ruby/1.9.1/rake/application.rb:94:in `each'
/usr/lib/ruby/1.9.1/rake/application.rb:94:in `block in top_level'
/usr/lib/ruby/1.9.1/rake/application.rb:133:in `standard_exception_handling'
/usr/lib/ruby/1.9.1/rake/application.rb:88:in `top_level'
/usr/lib/ruby/1.9.1/rake/application.rb:66:in `block in run'
/usr/lib/ruby/1.9.1/rake/application.rb:133:in `standard_exception_handling'
/usr/lib/ruby/1.9.1/rake/application.rb:63:in `run'
/usr/bin/rake:32:in `<main>'
Tasks: TOP => redmine:migrate_from_trac
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