Problem with multiple action for one armature

Hello evrybody. I’ll try to explain the problem in the better english i can.
I made an armature for a man character. I want to have indipendent animations for arms and legs, so I made a walk action for the legs without inserting keyframes for the arms bones and an action for the movents of the arms without touching the bones of the legs. If I put the actions together with logic bricks the final animation comes good and fluid. But if I activate the actions with a script, one of the two action (in this case the action of the legs) is not fluid and it is interrupted in the end, and the final animation is not fluid.
What is the problem? Why the activation of the actions with the script is not the same that the logic bricks?

Thank you for ansewers and sorry for my english!