Redmine

Hello all,
soory for my english i am french lol.
I did the upgrade from version 8 using the svn and prevents it from starting redmine via mongrel_cluster
returning to a previous version already old in 2568
it works

Daemonized, any open files are closed.  Look at /var/run/mongrel-cluster/mongrel.8001.pid and log/mongrel.8001.log for in$
** Starting Mongrel listening at 127.0.0.1:8001
** Initiating groups for "redmine":"www-data".
** Changing group to "www-data".
** Changing user to "redmine".
** Starting Rails with production environment...
/var/www/sa/redmine/config/../vendor/plugins/engines/lib/engines/assets.rb:20:in `initialize': Permission denied - /var/www/sa/redmine/public/plugin_assets/README (Errno::EACCES)
        from /var/www/sa/redmine/config/../vendor/plugins/engines/lib/engines/assets.rb:20:in `open'
        from /var/www/sa/redmine/config/../vendor/plugins/engines/lib/engines/assets.rb:20:in `initialize_base_public_direct$
        from /var/www/sa/redmine/config/../vendor/plugins/engines/lib/engines.rb:86:in `init'
        from /var/www/sa/redmine/vendor/plugins/engines/init.rb:4:in `evaluate_init_rb'
        from /var/lib/gems/1.8/gems/rails-2.1.2/lib/initializer.rb:476:in `call'
        from /var/lib/gems/1.8/gems/rails-2.1.2/lib/initializer.rb:476:in `after_initialize'
        from /var/lib/gems/1.8/gems/rails-2.1.2/lib/initializer.rb:475:in `each'
        from /var/lib/gems/1.8/gems/rails-2.1.2/lib/initializer.rb:475:in `after_initialize'
        from /var/lib/gems/1.8/gems/rails-2.1.2/lib/initializer.rb:152:in `process'
        from /var/lib/gems/1.8/gems/rails-2.1.2/lib/initializer.rb:97:in `send'
        from /var/lib/gems/1.8/gems/rails-2.1.2/lib/initializer.rb:97:in `run'
        from /var/www/sa/redmine/config/environment.rb:20
        from /usr/lib/ruby/1.8/rubygems/custom_require.rb:27:in `gem_original_require'
        from /usr/lib/ruby/1.8/rubygems/custom_require.rb:27:in `require'
        from /usr/lib/ruby/1.8/mongrel/rails.rb:147:in `rails'
        from /usr/bin/mongrel_rails:114:in `cloaker_'
        from /usr/lib/ruby/1.8/mongrel/configurator.rb:149:in `call'
        from /usr/lib/ruby/1.8/mongrel/configurator.rb:149:in `listener'
        from /usr/bin/mongrel_rails:100:in `cloaker_'
        from /usr/lib/ruby/1.8/mongrel/configurator.rb:50:in `call'
        from /usr/lib/ruby/1.8/mongrel/configurator.rb:50:in `initialize'
        from /usr/bin/mongrel_rails:85:in `new'
        from /usr/bin/mongrel_rails:85:in `run'
        from /usr/lib/ruby/1.8/mongrel/command.rb:212:in `run'
        from /usr/bin/mongrel_rails:282

thank you in advance to solve my problem