Comment 5 for bug 1195474

The kernel version 3.8.0-19 sounds like the initially released kernel. There has been an inquiry about some xen related network patches by Matt Wilson on the xen-devel mailing list this morning. I looked for the patches and those have been applied and released with the 3.8.0-28.41 kernel (or higher).
Btw, the Raring release recently went out of support (the first of the non-LTS releases with reduced duration of maintenance). The kernel currently gets a bit longer support but only as a hardware enablement option under Precise / 12.04).