I haven't looked into the history of the "--address" option for virsh
attach-disk, but 0.7.5 is *very* old, so it's completely possible that
it doesn't support that option. Can you upgrade to something more
modern? (libvirt is now at 1.0.4, and most distros are using at least
0.9.something or 0.10.something)

I was running on Ubuntu 10.04.4 LTS. I have now upgraded to Ubuntu 12.04.2 LTS.

"Address" seems to be in this newer version. Thanks for that!

However, now I cannot even add disks at all to the virtual servers.

If you look at the flow bellow, you see that I start a virtual server, removes a disk and then tries to add it again (using 2 methods).

First method (attach-device) just sits there forever and I have to cancel it.

The second method (attach-disk) timeouts after some time.

The log-file just states:
2013-04-09 22:35:57.000+0000: 6203: error : qemuDomainObjBeginJobInternal:789 : Timed out during operation: cannot acquire state change lock

I assume this means that libvirt cannot contact the QEMU monitor? How can I test that the QEMU monitor is still responding? Is there a way to bypass libvirt and send commands to QEMU Monitor manually?

(root@h2)-(/root)# virsh --version
0.9.8
(root@h2)-(/root)# kvm --version
QEMU emulator version 1.0 (qemu-kvm-1.0), Copyright (c) 2003-2008 Fabrice Bellard

(root@h2)-(/root)# virsh list --all
 Id Name                 State
----------------------------------
  7 dns                  running
  8 limelayer            running
  9 php3                 running
  - vps_99               shut off

(root@h2)-(/root)# virsh start vps_99
Domain vps_99 started

(root@h2)-(/root)# virsh list --all
 Id Name                 State
----------------------------------
  7 dns                  running
  8 limelayer            running
  9 php3                 running
 10 vps_99               running

(root@h2)-(/root)# virsh dumpxml vps_99
<domain type='kvm' id='10'>
  <name>vps_99</name>
  <uuid>d2eb6328-f288-1030-84c5-0050560018a2</uuid>
  <memory>1048576</memory>
  <currentMemory>1048576</currentMemory>
  <vcpu>2</vcpu>
  <os>
    <type arch='x86_64' machine='pc-1.0'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>restart</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/bin/kvm</emulator>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw'/>
      <source dev='/dev/nbd3'/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </disk>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw'/>
      <source dev='/dev/nbd1'/>
      <target dev='vdb' bus='virtio'/>
      <alias name='virtio-disk1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </disk>
    <interface type='bridge'>
      <mac address='00:50:56:00:1b:24'/>
      <source bridge='br0'/>
      <target dev='vnet3'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </interface>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='5999' autoport='no' keymap='en-us'/>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    </video>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </memballoon>
  </devices>
  <seclabel type='dynamic' model='apparmor' relabel='yes'>
    <label>libvirt-d2eb6328-f288-1030-84c5-0050560018a2</label>
    <imagelabel>libvirt-d2eb6328-f288-1030-84c5-0050560018a2</imagelabel>
  </seclabel>
</domain>

(root@h2)-(/root)# virsh detach-disk vps_99 vdb
Disk detached successfully

(root@h2)-(/root)# cat /tmp/disk.xml
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw'/>
      <source dev='/dev/nbd1'/>
      <target dev='vdb' bus='virtio'/>
      <alias name='virtio-disk1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </disk>

(root@h2)-(/root)# virsh attach-device vps_99 /tmp/disk.xml
^C
(root@h2)-(/root)# virsh list --all
 Id Name                 State
----------------------------------
  7 dns                  running
  8 limelayer            running
  9 php3                 running
 10 vps_99               running

(root@h2)-(/root)# virsh attach-disk vps_99 /dev/nbd1 vdb
error: Failed to attach disk
error: Timed out during operation: cannot acquire state change lock

Regards,
Daniele