This can be reproduced as follows:
1. Boot a VM
2. Wait till active
3. Snapshot the VM
4. Before snapshot comes to active, delete the vm 

2012-10-09 16:41:50 ERROR nova.openstack.common.rpc.amqp [-] Exception during message handling
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp Traceback (most recent call last):
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/nova/openstack/common/rpc/amqp.py", line 275, in _process_data
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     rval = self.proxy.dispatch(ctxt, version, method, **args)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/nova/openstack/common/rpc/dispatcher.py", line 145, in dispatch
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     return getattr(proxyobj, method)(ctxt, **kwargs)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/nova/exception.py", line 117, in wrapped
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     temp_level, payload)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/contextlib.py", line 24, in __exit__
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     self.gen.next()
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/nova/exception.py", line 92, in wrapped
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     return f(*args, **kw)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 210, in decorated_function
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     instance_uuid, e, sys.exc_info())
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/contextlib.py", line 24, in __exit__
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     self.gen.next()
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 199, in decorated_function
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     return function(self, context, *args, **kwargs)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1140, in snapshot_instance
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     self.driver.snapshot(context, instance, image_id)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/nova/exception.py", line 117, in wrapped
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     temp_level, payload)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/contextlib.py", line 24, in __exit__
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     self.gen.next()
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/nova/exception.py", line 92, in wrapped
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     return f(*args, **kw)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py", line 796, in snapshot
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     virt_dom.managedSave(0)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/eventlet/tpool.py", line 187, in doit
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     result = proxy_call(self._autowrap, f, *args, **kwargs)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/eventlet/tpool.py", line 147, in proxy_call
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     rv = execute(f,*args,**kwargs)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/eventlet/tpool.py", line 76, in tworker
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     rv = meth(*args,**kwargs)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/dist-packages/libvirt.py", line 696, in managedSave
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp     if ret == -1: raise libvirtError ('virDomainManagedSave() failed', dom=self)
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp libvirtError: operation failed: domain is no longer running
2012-10-09 16:41:50 TRACE nova.openstack.common.rpc.amqp