Open Stack

Hi,
I have a running instance and I'm not able to delete it. It is the tty 
img proposed here:
https://fedoraproject.org/wiki/Getting_started_with_OpenStack_Nova#Images

Note that new instances of this image work (can start-up and shutting-down).

Now the problem is that I'm not able to delete it.
- several time "euca-terminate-instance" did not work without any error 
message

[mex at minicloud cred]$ euca-describe-instances
RESERVATION     r-6xvr06s5      mex     default
INSTANCE        i-00000004      ami-00000003    10.0.0.3        
10.0.0.3        running nova_key (mex, minicloud.di.unipmn.it)  
0               m1.small        2012-05-30T13:21:27Z    nova    
aki-00000001    ari-00000002
[mex at minicloud cred]$ euca-terminate-instances i-00000004
[mex at minicloud cred]$ euca-describe-instances
RESERVATION     r-6xvr06s5      mex     default
INSTANCE        i-00000004      ami-00000003    10.0.0.3        
10.0.0.3        running nova_key (mex, minicloud.di.unipmn.it)  
0               m1.small        2012-05-30T13:21:27Z    nova    
aki-00000001    ari-00000002


- several time "nova delete <id>" without success:

[mex at minicloud cred]$ nova list
+----+----------+--------+--------------+
| ID |   Name   | Status |   Networks   |
+----+----------+--------+--------------+
| 4  | Server 4 | ACTIVE | mex=10.0.0.3 |
+----+----------+--------+--------------+
[mex at minicloud cred]$ nova delete 4
[mex at minicloud cred]$ nova list
+----+----------+--------+--------------+
| ID |   Name   | Status |   Networks   |
+----+----------+--------+--------------+
| 4  | Server 4 | ACTIVE | mex=10.0.0.3 |
+----+----------+--------+--------------+

- reboot: right now, I have openstack installed/configured in one 
machine. I tried to reboot it and nothing has changed.

Any suggestion, please?

Massimo