A look at the Data Protector Virtualization support matrix
http://support.openview.hp.com/selfsolve/document/KM1357659
show this for Xen
Citrix - Citrix XenServer 4.1, 5.0, 5.5, 5.6, 6.0
I guess that 6.0.2 was not enough of a difference from 6.0 to matter to Data Protector, but, when you upgraded to Xen 6.2, it became an unsupported configuration. I would imagine that it will be supported in the future, I have no idea of when
I suggest that you Bookmark the above URL, and check the support matrix periodically