Hello BachPham.
I found the solution.
At first hand, before to install acymailing, deactivate k2 autotwitter component and plugin.
Second, install acymailing and configurate it!!
Third, don't activate AcyMailing : (auto)Subscribe during Joomla registration plugin and CB user registration plugin too.
Fourth, activate again k2 autotwitter component and plugin.
Fiveth, clear install cache for acymailing and k2 autotwitter
Sixth, all work again fine!!!!
Hiphotesis, block access to k2 item content by to diferents components&plugins access methods.
Thanks BachPham for your fast reply, but it's working now!!