Unknown Client Error syncronizing

In some cases, when we do a sync to server, in the rhoconnect server log appears the following error:

[10:21:25 AM 2012-06-27] Unknown client/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/client_sync.rb:11:in `initialize'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/server.rb:159:in `new'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/server.rb:159:in `current_client_sync'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/api/application/query.rb:4:in `block (2 levels) in <top (required)>'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/async.rb:41:in `block in catch_all'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/async.rb:41:in `catch'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/async.rb:41:in `catch_all'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/api/application/query.rb:2:in `block in <top (required)>'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/async.rb:56:in `block (2 levels) in execute_api_call'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/async.rb:41:in `block in catch_all'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/async.rb:41:in `catch'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/async.rb:41:in `catch_all'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/rhoconnect-3.2.1/lib/rhoconnect/async.rb:55:in `block in execute_api_call'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/eventmachine-0.12.10/lib/eventmachine.rb:1060:in `call'

/opt/rhoconnect/lib/ruby/gems/1.9.1/gems/eventmachine-0.12.10/lib/eventmachine.rb:1060:in `block in spawn_threadpool'

What's the problem?

Thanks,

Oesia