It is nothing to do with root. Installs fine on rooted phones. However it is a patch update and checks for/expects certain stock Vodafone files to be in place, unchanged before it updates them. It also requires stock recovery and not CWM - or at least it did for me. Once you run the update with stock recovery you should get a log telling you which file it failed on.
Edited by Hogweed, 07 August 2012 - 04:17 PM.