I've found the problem with message arguments parsing.
Maybe it is because of TUIO protocol changes, dunno

It definetely happens when I check 'send width & height' in CCV.
As I understand in this case CCV sends more data in messages.

I hacked the code to see arguments, there are actually 2 more arguments.

Maybe limiting arguments array size is the solution (tuio_client.rb:42)

here is a dump:

./tuio-ruby/lib/tuio-ruby/tuio_client.rb:91:in initialize': wrong number of arguments (8 for 6) (ArgumentError) from ./tuio-ruby/lib/tuio-ruby/tuio_client.rb:91:innew'
from ./tuio-ruby/lib/tuio-ruby/tuio_client.rb:91:in track_tuio_cursor' from ./tuio-ruby/lib/tuio-ruby/tuio_client.rb:42:ininitialize'
from XXXXXXX/ruby/lib/ruby/gems/1.8/gems/osc-ruby-0.2.0/lib/osc-ruby/server.rb:50:in call' from XXXXXXX/ruby/lib/ruby/gems/1.8/gems/osc-ruby-0.2.0/lib/osc-ruby/server.rb:50:insendmesg'
from XXXXXXX/ruby/lib/ruby/gems/1.8/gems/osc-ruby-0.2.0/lib/osc-ruby/server.rb:48:in each' from XXXXXXX/ruby/lib/ruby/gems/1.8/gems/osc-ruby-0.2.0/lib/osc-ruby/server.rb:48:insendmesg'
from XXXXXXX/ruby/lib/ruby/gems/1.8/gems/osc-ruby-0.2.0/lib/osc-ruby/server.rb:80:in dispatch_message' ... 8 levels... from ./tuio-ruby/lib/tuio-ruby/tuio_client.rb:52:ininitialize'
from ./tuio-ruby/lib/tuio-ruby/tuio_client.rb:52:in new' from ./tuio-ruby/lib/tuio-ruby/tuio_client.rb:52:instart'
from ctrl_server.rb:34

I'm running ubuntu 9.04 with ruby 1.8.7
Got installed tuio-ruby 0.2.2 gem by 'gem install tuio-ruby' and osc-ruby 0.2.0

simple example with slightly modified copy-paste of your example.rb doesn't work.
btw, original example.rb doesn't work as well

Looks like requires in 'lib/tuio_client.rb' should be changed to something like these:

core exts

require File.join( File.dirname( FILE ), 'core_ext', 'object' )
require File.join( File.dirname( FILE ), 'core_ext', 'float' )

my code:

require 'rubygems'
require 'tuio-ruby'
@tc = TuioClient.new

@tc.on_object_creation do | to |
puts "New TUIO Object at x: #{to.x_pos}, y: #{to.y_pos}"
end

@tc.on_object_update do | to |
puts "Updated TUIO Object #{to.fiducial_id} at x: #{to.x_pos}, y: #{to.y_pos}"
end

@tc.on_object_removal do | to |
puts "Removed TUIO Object #{to.fiducial_id}"

end

The error:
/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require': no such file to load -- core_ext/object (LoadError) from /usr/lib/ruby/1.8/rubygems/custom_require.rb:31:inrequire'
from /home/test/.gem/ruby/1.8/gems/tuio-ruby-0.2.2/lib/tuio-ruby/tuio_client.rb:5
from /usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require' from /usr/lib/ruby/1.8/rubygems/custom_require.rb:31:inrequire'
from /home/test/.gem/ruby/1.8/gems/tuio-ruby-0.2.2/lib/tuio-ruby.rb:10
from /usr/lib/ruby/1.8/rubygems/custom_require.rb:36:in gem_original_require' from /usr/lib/ruby/1.8/rubygems/custom_require.rb:36:inrequire'
from ruby_test.rb:2