is this the full stacktrace? Strange that this is on the level 'INFO'.

Can you raise (lower?) the log level to debug and see what happens and post that.

no, jdk logging is used, but I think it ends up in the log4j of jboss

I get the same thing trying to run a ProcessDefinitionQuery:

org.jbpm.jpdl.internal.model.JpdlProcessDefinition cannot be cast to java.util.List
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1338)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:473)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
 at java.security.AccessController.doPrivileged(Native Method)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)
 at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)
 at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
 at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)
 at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
 at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
 at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429)
 at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728)
 at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380)
 at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255)
 at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199)
 at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45)
 at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3830)
 at org.apache.catalina.core.StandardContext.start(StandardContext.java:4337)
 at org.apache.catalina.manager.ManagerServlet.start(ManagerServlet.java:1237)
 at org.apache.catalina.manager.HTMLManagerServlet.start(HTMLManagerServlet.java:591)
 at org.apache.catalina.manager.HTMLManagerServlet.doGet(HTMLManagerServlet.java:128)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:525)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:263)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
 at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:584)
 at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
 at java.lang.Thread.run(Thread.java:637)
Caused by: java.lang.ClassCastException: org.jbpm.jpdl.internal.model.JpdlProcessDefinition cannot be cast to java.util.List
 at org.jbpm.pvm.internal.repository.ProcessDeployer.deploy(ProcessDeployer.java:64)
 at org.jbpm.pvm.internal.repository.DeployerManager.deploy(DeployerManager.java:46)
 at org.jbpm.pvm.internal.repository.RepositorySessionImpl.getObject(RepositorySessionImpl.java:120)
 at org.jbpm.pvm.internal.query.ProcessDefinitionQueryImpl.execute(ProcessDefinitionQueryImpl.java:72)
 at org.jbpm.pvm.internal.query.AbstractQuery.execute(AbstractQuery.java:81)
 at org.jbpm.pvm.internal.svc.DefaultCommandService.execute(DefaultCommandService.java:42)
 at org.jbpm.pvm.internal.spring.CommandTransactionCallback.doInTransaction(CommandTransactionCallback.java:50)
 at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:128)
 at org.jbpm.pvm.internal.tx.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:77)
 at org.jbpm.pvm.internal.svc.EnvironmentInterceptor.execute(EnvironmentInterceptor.java:46)
 at org.jbpm.pvm.internal.svc.RetryInterceptor.execute(RetryInterceptor.java:55)
 at org.jbpm.pvm.internal.query.AbstractQuery.untypedList(AbstractQuery.java:62)
 at org.jbpm.pvm.internal.query.ProcessDefinitionQueryImpl.list(ProcessDefinitionQueryImpl.java:141)

Envoronment:
windows vista
apache-tomcat-6.0.20
jbpm 4.1
hsqldb

If one replaces the line 64 in the org.jbpm.pvm.internal.repository.ProcessDeployer:

List<ProcessDefinitionImpl> processDefinitions = (List<ProcessDefinitionImpl>) parse.getDocumentObject();

List<ProcessDefinitionImpl> processDefinitions = new java.util.ArrayList<ProcessDefinitionImpl>();
Object obj = parse.getDocumentObject();
if (obj instanceof java.util.ArrayList)
{
 processDefinitions = (List<ProcessDefinitionImpl>)obj;
}
else
{
 processDefinitions.add((ProcessDefinitionImpl)obj);
}