Project actuals error when modifying TASK_PCT_WORK_COMP through PSI

I've been working a few hours trying to modify the percent work complete on a task. I've been working with TASK_PCT_WORK, TASK_WORK (read only), TASK_ACT_WORK and TASK_REM_WORK.
As you will know the percent complete of a task can be modifyed directly (using PSI) from TASK_PCT_WORK_COMP column but today, in a new installation of Project Server, I receive an error from the queue saying ProjectActualsAreBlocked. After a few hours trying to find what does that error means I have found modifying the project from Project Professional that I couldn't modify the percent of task completed saying the same error. Project Professional gave me the clue saying that task work could only be modifyed through Project Web Access. So if you acces server setting in PWA will find that under task settings and display there is an option (which is maked as default) called "Restrict updates to Project Web Access". When I uncheked this option I could modify TASK_PCT_WORK_COMP from PSI.