I can only guess how you do the deployment since you do not tell. But if you are using the Deployment tab of the processdefinition in eclipse then you can select the stuff to deploy. Unfortunately the ActionHandlers are not selected by default and I have to do the selection on every deployment. But as far as I don't forget this it works.
Perhaps you have to provide more info.
You are right, I'm deploying using Eclipse. Sorry for no give this information in the first post :(
I did the sequence of operations below:
1 - Deploy a process that has one action, (Before deploy the process I cleared my database);
2 - Next I change the behaviour of this action;
3 - An after I start a process instance;
4 - So I checked that the new altered code of action was executed. The version stored in database wasn't executed.
I notice the problem of deploying ActionHandlers, mine aren't all selected too. Despite the actions are in the process definition.
what do you do between 2 and 3? Nothing? Then surely your old processdefinition will use the old actions. Even if you deploy the new definition including new actions, old processdefinitions will still use the old actions.