I'm getting the same Error. Did you find any solution yet?
Unfortunately not yet. I'm trying to migrate to jboss 7, to upgrade hibernate version
I solved this issue,
in persistence.xml I had : <mapping-file>META-INF/ProcessInstanceInfo.hbm.xml</mapping-file>
and I added the ProcessInstanceInfo.hbm.xml file in the same place as persistence.xml.
what I did'nt know jbpm-persistence-jpa-5.3.0.Final.jar comes with it's oun ProcessInstanceInfo.hbm.xml file,
So by changing the name of the file ProcessInstanceInfo.hbm.xml to (ProcessInstanceInfo_P.hbm.xml) in the folder META-INF of my project
and adding <mapping-file>META-INF/ProcessInstanceInfo_P.hbm.xml</mapping-file> (remove the old one) in my persistence.xml
and changing in ProcessInstanceInfo_P.hbm.xml file:
<property name="processInstanceByteArray" type="org.jbpm.persistence.processinstance.BlobUserType" column="processInstanceByteArray" access="field" length="2147483647" />
<property name="processInstanceByteArray" type="org.hibernate.type.PrimitiveByteArrayBlobType" access="field" > <column name="processInstanceByteArray" sql-type="oid"/> </property>
this fix my issue