Logstash error

Fail to flush

Failed to flush outgoing items {:outgoing_count=>100, :exception=>#<Encoding::InvalidByteSequenceError: ""\xC0"" on ASCII-8BIT>, :backtrace=>["org/jruby/RubyString.java:7599:in `encode'", "json/ext/GeneratorMethods.java:71:in `to_json'", "file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/logstash/event.rb:168:in `to_json'", "jar:file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/logstash/outputs/elasticsearch.rb:322:in `flush'", "org/jruby/RubyArray.java:1613:in `each'", "jar:file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/logstash/outputs/elasticsearch.rb:310:in `flush'", "jar:file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/stud/buffer.rb:219:in `buffer_flush'", "org/jruby/RubyHash.java:1338:in `each'", "jar:file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/stud/buffer.rb:216:in `buffer_flush'", "jar:file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/stud/buffer.rb:193:in `buffer_flush'", "jar:file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/stud/buffer.rb:159:in `buffer_receive'", "jar:file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/logstash/outputs/elasticsearch.rb:305:in `receive'", "file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/logstash/outputs/base.rb:86:in `handle'", "(eval):41:in `initialize'", "org/jruby/RubyProc.java:271:in `call'", "file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/logstash/pipeline.rb:259:in `output'", "file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/logstash/pipeline.rb:218:in `outputworker'", "file:/home/aaron/Downloads/logstash-1.3.2-flatjar.jar!/logstash/pipeline.rb:145:in `start_outputs'"], :level=>:warn}