Driver Error message when Updating XenTools

When updating from XenServer 6.5 SP1 to 7.0 (all updates until 29 included) and upgrading XenTools, I always get that error message popping up:

It just seems to be some blemish, because everything works and after 2 reboots VMs are shown as optimized in XenCenter, but I was worried the first time, I've seen it.
(from experience, I start upgrading with less important VMs and see if everything runs smooth)

Regards

• Christof