An upgrade to Debian 6.0.7 was installed last night across all servers.
This work appears to have been successful and no adverse side-effects have been observed as at this time.
Debian 6.0.7 includes an update to the Xen hypervisor and Linux kernel binaries. To activate these, a reboot of the Xen server stack will be required. This will be scheduled shortly and an email will be sent to all affected clients.