Which version of jBPM are you using?
Which Hadler are you attaching to the "Service Task" you are using?
I use 5.1 and i coded a handler which implements workitemhandler
I found it. I forgot to execute completeWorkItem() on the WorkItemManager at the end of my executeWorkItem method. Obviously thats needed to be done?
Excatly! Depending whether you are implementinc syncronous or asynchronous behavior, you need complete the WI inside its handler or not.
Maybe this could help you to understand how WI work: http://community.jboss.org/message/600431#600431