Logstash stops itself

Hello,

Every 1/2 weeks i'm finding my logstash stopped.
I check logstas.err and it show this log:

Non US-ASCII detected and no charset defined.
Defaulting to UTF-8, set your own if this is incorrect.
Non US-ASCII detected and no charset defined.
Defaulting to UTF-8, set your own if this is incorrect.
RuntimeError: can't add a new key into hash during iteration
[]= at org/jruby/RubyHash.java:992
filter at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-filter-throttle-2.0.2/lib/logstash/filters/throttle.rb:186
multi_filter at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/filters/base.rb:152
each at org/jruby/RubyArray.java:1613
multi_filter at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/filters/base.rb:149
cond_func_264 at (eval):5682
each at org/jruby/RubyArray.java:1613
cond_func_264 at (eval):5678
cond_func_263 at (eval):5702
each at org/jruby/RubyArray.java:1613
cond_func_263 at (eval):5699
filter_func at (eval):1244
filterworker at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/pipeline.rb:219
start_filters at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/pipeline.rb:154

Does anybody knows why it is happening to my installation? how can i fix it?

Thanks