Why I can not update some properties of running VMs?

Issue

• When I try to edit any property of a running VM I'm presented with the following error:

<vm_name>:

    Failed updating the properties of the VM. This may be caused either by:
    1. The values selected are not appropriate for the VM; or
    2. Its values cannot be updated while the VM is in UP state (Please shut down the VM in order to modify properties such as CPU or cluster).

• /var/log/ovirt-engine/engine.log log file shows the following error messages:

2013-08-23 10:06:59,709 ERROR [org.ovirt.engine.core.utils.ObjectIdentityChecker] (ajp-/127.0.0.1:8702-15) [de80ed8] Field timeZone can not be updated when status is Up
2013-08-23 10:06:59,709 WARN  [org.ovirt.engine.core.utils.ObjectIdentityChecker] (ajp-/127.0.0.1:8702-15) [de80ed8] ObjectIdentityChecker.IsUpdateValid:: Not updatable field 'timeZone' was updated
2013-08-23 10:06:59,709 WARN  [org.ovirt.engine.core.bll.UpdateVmCommand] (ajp-/127.0.0.1:8702-15) [de80ed8] CanDoAction of action UpdateVm failed. Reasons:VAR__ACTION__UPDATE,VAR__TYPE__VM,VM_CANNOT_UPDATE_ILLEGAL_FIELD