Redmine

I have set up the redmine-2.1.0 but facing issue while configuring the redmine with mongrel cluster

Here is the error that found in the log file of mongrel

/var/lib/gems/1.8/gems/activesupport-3.2.8/lib/active_support/dependencies.rb:251:in `require': no such file to load -- dispatcher (LoadError)
from /var/lib/gems/1.8/gems/activesupport-3.2.8/lib/active_support/dependencies.rb:251:in `require'
from /var/lib/gems/1.8/gems/activesupport-3.2.8/lib/active_support/dependencies.rb:236:in `load_dependency'
from /var/lib/gems/1.8/gems/activesupport-3.2.8/lib/active_support/dependencies.rb:251:in `require'
from /var/lib/gems/1.8/gems/mongrel-1.2.0.pre2/bin/../lib/mongrel/rails.rb:148:in `rails'
from /var/lib/gems/1.8/gems/mongrel-1.2.0.pre2/bin/mongrel_rails:116:in `cloaker_'
from /var/lib/gems/1.8/gems/mongrel-1.2.0.pre2/bin/../lib/mongrel/configurator.rb:149:in `call'
from /var/lib/gems/1.8/gems/mongrel-1.2.0.pre2/bin/../lib/mongrel/configurator.rb:149:in `listener'
from /var/lib/gems/1.8/gems/mongrel-1.2.0.pre2/bin/mongrel_rails:102:in `cloaker_'
from /var/lib/gems/1.8/gems/mongrel-1.2.0.pre2/bin/../lib/mongrel/configurator.rb:50:in `call'
from /var/lib/gems/1.8/gems/mongrel-1.2.0.pre2/bin/../lib/mongrel/configurator.rb:50:in `initialize'
from /var/lib/gems/1.8/gems/mongrel-1.2.0.pre2/bin/mongrel_rails:86:in `new'
from /var/lib/gems/1.8/gems/mongrel-1.2.0.pre2/bin/mongrel_rails:86:in `run'
from /var/lib/gems/1.8/gems/mongrel-1.2.0.pre2/bin/../lib/mongrel/command.rb:210:in `run'
from /var/lib/gems/1.8/gems/mongrel-1.2.0.pre2/bin/mongrel_rails:282
from /var/lib/gems/1.8/bin/mongrel_rails:19:in `load'
from /var/lib/gems/1.8/bin/mongrel_rails:19
Please help me