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:in `json_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:in `each'
    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:in `json_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:in
`to_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:in `map'
    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:in `to_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:in `render_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:in `realtime'
    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:in `index'
    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:in `perform_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:in `perform_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:in `measure'
    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:in `perform_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
n `cache'
    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:in `perform_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:in `process_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:in `process'
    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:in `handle_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:in `synchronize'
    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:in `dispatch_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:in `process'
    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:in `process'
    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:in `each'
    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:in `run'
    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:in `new'
    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:in `initialize'
    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:in `run'
    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:in `each'
    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:in `run'
    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:in `load'
    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:in `new_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:in
`gem_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:in `require'
    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:in `require'
    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'