Error in setting dates with RubyOSA

>> require 'rbosa'
=> true
>> t = OSA.app('iTunes')
=> <OSA::ITunes::Application:0x10151ce88 desc="'sign'($6B6F6F68$)">
>> track = t.current_track
=> <OSA::ITunes::Track:0x101519a58 desc="'obj '{ 'want':'prop', 'from':'null'(), 'form':'prop', 'seld':'pTrk' }">
>> track.name
=> "The Way I Are"
>> track.played_count
=> 1
>> track.played_date = Time.now.to_i
RuntimeError: application returned error: A descriptor type mismatch occurred. (-10001)
	from /usr/local/lib/ruby/site_ruby/1.8/rbosa.rb:547:in `__send_event__'
	from /usr/local/lib/ruby/site_ruby/1.8/rbosa.rb:547:in `played_date='
	from (irb):7
>> track.played_date = Date.today
RuntimeError: application returned error: A descriptor type mismatch occurred. (-10001)
	from /usr/local/lib/ruby/site_ruby/1.8/rbosa.rb:547:in `__send_event__'
	from /usr/local/lib/ruby/site_ruby/1.8/rbosa.rb:547:in `played_date='
	from (irb):8
>> track.played_date = Time.now
RuntimeError: application returned error: A descriptor type mismatch occurred. (-10001)
	from /usr/local/lib/ruby/site_ruby/1.8/rbosa.rb:547:in `__send_event__'
	from /usr/local/lib/ruby/site_ruby/1.8/rbosa.rb:547:in `played_date='
	from (irb):9



OSX Snow Leopard
ruby 1.8.7 (2009-06-12 patchlevel 174) [i686-darwin10.0.0]