Why doesn't json pure work in Rails?

installed json_pure 1.1.2 and whenever Rails calls to_json on a model
I get the following error:

ArgumentError (wrong number of arguments (2 for 1)):
c:/ruby/lib/ruby/gems/1.8/gems/json_pure-1.1.2/lib/json/pure/
generator.rb:251:in to_json' c:/ruby/lib/ruby/gems/1.8/gems/json_pure-1.1.2/lib/json/pure/ generator.rb:251:injson_transform’
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.1.0/lib/
active_record/attribute_methods.rb:211:in map' c:/ruby/lib/ruby/gems/1.8/gems/json_pure-1.1.2/lib/json/pure/ generator.rb:245:ineach’
c:/ruby/lib/ruby/gems/1.8/gems/json_pure-1.1.2/lib/json/pure/
generator.rb:245:in map' c:/ruby/lib/ruby/gems/1.8/gems/json_pure-1.1.2/lib/json/pure/ generator.rb:245:injson_transform’
c:/ruby/lib/ruby/gems/1.8/gems/json_pure-1.1.2/lib/json/pure/
generator.rb:218:in to_json' /vendor/plugins/appcelerator/lib/appcelerator/extensions.rb:35:into_json’
c:/ruby/lib/ruby/gems/1.8/gems/json_pure-1.1.2/lib/json/pure/
generator.rb:300:in json_transform' c:/ruby/lib/ruby/gems/1.8/gems/json_pure-1.1.2/lib/json/pure/ generator.rb:299:inmap’
c:/ruby/lib/ruby/gems/1.8/gems/json_pure-1.1.2/lib/json/pure/
generator.rb:299:in json_transform' c:/ruby/lib/ruby/gems/1.8/gems/json_pure-1.1.2/lib/json/pure/ generator.rb:272:into_json’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/base.rb:888:in render_with_no_layout' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/ action_controller/layout.rb:259:inrender_without_benchmark’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/benchmarking.rb:51:in render' c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.0/lib/ active_support/core_ext/benchmark.rb:8:inrealtime’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/benchmarking.rb:51:in render' /app/controllers/getthere_bookings_controller.rb:4:inindex’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/base.rb:1162:in send' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/ action_controller/base.rb:1162:inperform_action_without_filter
s’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/filters.rb:580:in call_filters' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/ action_controller/filters.rb:573:inperform_action_without_benc
hmark’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/benchmarking.rb:68:in perform_action_without_ rescue' c:/ruby/lib/ruby/1.8/benchmark.rb:293:inmeasure’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/benchmarking.rb:68:in perform_action_without_ rescue' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/ action_controller/rescue.rb:201:inperform_action_without_cachi
ng’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/caching/sql_cache.rb:13:in perform_action' c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.1.0/lib/ active_record/connection_adapters/abstract/query_cache.rb:33:i ncache’
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.1.0/lib/
active_record/query_cache.rb:8:in cache' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/ action_controller/caching/sql_cache.rb:12:inperform_action’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/base.rb:529:in send' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/ action_controller/base.rb:529:inprocess_without_filters’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/filters.rb:569:in process_without_session_man agement_support' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/ action_controller/session_management.rb:130:inprocess’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/base.rb:389:in process' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/ action_controller/dispatcher.rb:149:inhandle_request’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/dispatcher.rb:107:in dispatch' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/ action_controller/dispatcher.rb:104:insynchronize’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/dispatcher.rb:104:in dispatch' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/ action_controller/dispatcher.rb:120:indispatch_cgi’
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/
action_controller/dispatcher.rb:35:in dispatch' c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/bin/../ lib/mongrel/rails.rb:76:inprocess’
c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/bin/…/
lib/mongrel/rails.rb:74:in synchronize' c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/bin/../ lib/mongrel/rails.rb:74:inprocess’
c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/
mongrel.rb:159:in process_client' c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/ mongrel.rb:158:ineach’
c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/
mongrel.rb:158:in process_client' c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/ mongrel.rb:285:inrun’
c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/
mongrel.rb:285:in initialize' c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/ mongrel.rb:285:innew’
c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/
mongrel.rb:285:in run' c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/ mongrel.rb:268:ininitialize’
c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/
mongrel.rb:268:in new' c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/ mongrel.rb:268:inrun’
c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/
mongrel/configurator.rb:282:in run' c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/ mongrel/configurator.rb:281:ineach’
c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/
mongrel/configurator.rb:281:in run' c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/bin/ mongrel_rails:128:inrun’
c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/lib/
mongrel/command.rb:212:in run' c:/ruby/lib/ruby/gems/1.8/gems/mongrel-1.1.4-x86-mswin32-60/bin/ mongrel_rails:281 c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.0/lib/ active_support/dependencies.rb:502:inload’
c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.0/lib/
active_support/dependencies.rb:502:in load' c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.0/lib/ active_support/dependencies.rb:354:innew_constants_in’
c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.0/lib/
active_support/dependencies.rb:502:in load' c:/ruby/lib/ruby/gems/1.8/gems/rails-2.1.0/lib/commands/servers/ mongrel.rb:64 c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:ingem_original_require’
c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
require' c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.0/lib/ active_support/dependencies.rb:509:inrequire’
c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.0/lib/
active_support/dependencies.rb:354:in new_constants_in' c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.0/lib/ active_support/dependencies.rb:509:inrequire’
c:/ruby/lib/ruby/gems/1.8/gems/rails-2.1.0/lib/commands/server.rb:
39
c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
`gem_original_require’