I am having the same problem,
please take a look at my source attached, using jbpm 5.4 with as 7.1.1 too
My JbpmEJB bean is calling guvnor which works fine, the problem is when I am deploying the EAR file it gives me the same error as Albert's.
For the dependecies, I just added all the jar files inside the runtime folder...
Thanks,
John