Redmine

Hello, after upgrade the ubuntu server my redmine has broken. When I try to make new ticket or to change the ticket owner it gives me 500 Internal Server Error. The log msg below:

Sending email notification to:xxx@xxx.xx, xxxx@xxxx.xx
Sent mail to 

EOFError (end of file reached):
  /usr/lib/ruby/1.8/net/protocol.rb:135:in `sysread'
  /usr/lib/ruby/1.8/net/protocol.rb:135:in `rbuf_fill'
  /usr/lib/ruby/1.8/timeout.rb:67:in `timeout'
  /usr/lib/ruby/1.8/timeout.rb:101:in `timeout'
  /usr/lib/ruby/1.8/net/protocol.rb:134:in `rbuf_fill'
  /usr/lib/ruby/1.8/net/protocol.rb:116:in `readuntil'
  /usr/lib/ruby/1.8/net/protocol.rb:126:in `readline'
  /usr/lib/ruby/1.8/net/smtp.rb:923:in `recv_response'
  /usr/lib/ruby/1.8/net/smtp.rb:554:in `do_start'
  /usr/lib/ruby/1.8/net/smtp.rb:933:in `critical'
  /usr/lib/ruby/1.8/net/smtp.rb:554:in `do_start'
  /usr/lib/ruby/1.8/net/smtp.rb:525:in `start'
  app/models/mailer.rb:322:in `deliver!'
  app/models/issue_observer.rb:20:in `after_create'
  /usr/lib/ruby/1.8/observer.rb:185:in `notify_observers'
  /usr/lib/ruby/1.8/observer.rb:184:in `each'
  /usr/lib/ruby/1.8/observer.rb:184:in `notify_observers'
  app/controllers/issues_controller.rb:145:in `create'
  /usr/lib/ruby/1.8/webrick/httpserver.rb:104:in `service'
  /usr/lib/ruby/1.8/webrick/httpserver.rb:65:in `run'
  /usr/lib/ruby/1.8/webrick/server.rb:173:in `start_thread'
  /usr/lib/ruby/1.8/webrick/server.rb:162:in `start'
  /usr/lib/ruby/1.8/webrick/server.rb:162:in `start_thread'
  /usr/lib/ruby/1.8/webrick/server.rb:95:in `start'
  /usr/lib/ruby/1.8/webrick/server.rb:92:in `each'
  /usr/lib/ruby/1.8/webrick/server.rb:92:in `start'
  /usr/lib/ruby/1.8/webrick/server.rb:23:in `start'
  /usr/lib/ruby/1.8/webrick/server.rb:82:in `start'

Rendering /var/www/redmine/public/500.html (500 Internal Server Error)

Does anybody know what's wrong?