Description of problem:
trying to detach an iscsi lun from engine throws an exception, it fails casting:

2013-11-05 00:34:01,036 INFO  [org.ovirt.engine.core.bll.DetachDiskFromVmCommand] (ajp-/127.0.0.1:8702-5) [589f916b] Running command: DetachDiskFromVmCommand internal: false. Entities affected :  ID: a34a7871-1218-49d9-90d2-0976c0a37963 Type: VM
2013-11-05 00:34:01,038 ERROR [org.ovirt.engine.core.bll.DetachDiskFromVmCommand] (ajp-/127.0.0.1:8702-5) [589f916b] Command org.ovirt.engine.core.bll.DetachDiskFromVmCommand throw exception: java.lang.ClassCastException: org.ovirt.engine.core.common.businessentities.LunDisk cannot be cast to org.ovirt.engine.core.common.businessentities.DiskImage
        at org.ovirt.engine.core.bll.DetachDiskFromVmCommand.executeVmCommand(DetachDiskFromVmCommand.java:94) [bll.jar:]
        at org.ovirt.engine.core.bll.VmCommand.executeCommand(VmCommand.java:87) [bll.jar:]
        at org.ovirt.engine.core.bll.CommandBase.executeWithoutTransaction(CommandBase.java:1131) [bll.jar:]
        at org.ovirt.engine.core.bll.CommandBase.executeActionInTransactionScope(CommandBase.java:1216) [bll.jar:]
        at org.ovirt.engine.core.bll.CommandBase.runInTransaction(CommandBase.java:1892) [bll.jar:]
        at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInNewTransaction(TransactionSupport.java:210) [utils.jar:]
        at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInRequired(TransactionSupport.java:149) [utils.jar:]
        at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInScope(TransactionSupport.java:118) [utils.jar:]
        at org.ovirt.engine.core.bll.CommandBase.execute(CommandBase.java:1236) [bll.jar:]
        at org.ovirt.engine.core.bll.CommandBase.executeAction(CommandBase.java:362) [bll.jar:]
        at org.ovirt.engine.core.bll.Backend.runAction(Backend.java:416) [bll.jar:]
        at org.ovirt.engine.core.bll.Backend.runActionImpl(Backend.java:395) [bll.jar:]
        at org.ovirt.engine.core.bll.Backend.RunAction(Backend.java:353) [bll.jar:]
        at sun.reflect.GeneratedMethodAccessor159.invoke(Unknown Source) [:1.7.0_45]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [rt.jar:1.7.0_45]
        at java.lang.reflect.Method.invoke(Method.java:606) [rt.jar:1.7.0_45]
        at org.jboss.as.ee.component.ManagedReferenceMethodInterceptorFactory$ManagedReferenceMethodInterceptor.processInvocation(ManagedReferenceMethodInterceptorFactory.java:72) [jboss-as-ee.jar:7.3.0.Final-redhat-8]
        at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation.jar:1.1.2.Final-redhat-1]
        at org.jboss.invocation.WeavedInterceptor.processInvocation(WeavedInterceptor.java:53) [jboss-invocation.jar:1.1.2.Final-redhat-1]
        at org.jboss.as.ee.component.interceptors.UserInterceptorFactory$1.processInvocation(UserInterceptorFactory.java:58) [jboss-as-ee.jar:7.3.0.Final-redhat-8]
        at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation.jar:1.1.2.Final-redhat-1]
        at org.jboss.invocation.InterceptorContext$Invocation.proceed(InterceptorContext.java:374) [jboss-invocation.jar:1.1.2.Final-redhat-1]
        at org.ovirt.engine.core.bll.interceptors.ThreadLocalSessionCleanerInterceptor.injectWebContextToThreadLocal(ThreadLocalSessionCleanerInterceptor.java:13) [bll.jar:]
        at sun.reflect.GeneratedMethodAccessor16.invoke(Unknown Source) [:1.7.0_45]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [rt.jar:1.7.0_45]
        at java.lang.reflect.Method.invoke(Method.java:606) [rt.jar:1.7.0_45]
        at org.jboss.as.ee.component.ManagedReferenceLifecycleMethodInterceptorFactory$ManagedReferenceLifecycleMethodInterceptor.processInvocation(ManagedReferenceLifecycleMethodInterceptorFactory.java:123) [jboss-as-ee.jar:7.3.0.Final-redhat-8]