We've been changing the way we handle the virtual machine admin addresses, to enable them to be reached over IPv6 and this has lead to a temporary outage.
The outage should be resolved within the next 30 minutes.
For every virtual machine we provide out of band access, which allows you to halt, reboot, and perform other administrative work even if your machine is cut off from the network. If you have a virtual machine foo.vm.bytemark.co.uk then you can connect to the admin shell by using the hostname "foo.vmadmin.bytemark.co.uk".
These vmadmin addresses were solely available via IPv4 until today. We've changed this now so that the addresses will resolve to both IPv6 and IPv4 addresses. In the process we temporarily broke things, but they should be back shortly.
Further documentation on the vmshell is available online for reference.
This problem has now been resolved; and the *.vmadmin.bytemark.co.uk addresses will now be available for both IPv4 & IPv6.