Hi, sorry for the late reply as I thought it fixed it, but today it came back after I restarted the Veeam One server. Yes, the CPU goes when I turn off Veeam One.
Originally I fixed it by excluding all hosts and then adding them one at a time, as instructed by KB http://www.veeam.com/kb1649
So rebooted this morning, and I got a "Performance data collection failure" in Veeam One and by vcenter CPU is 100% again.
This must be a bug, as I shouldn't have to exclude all hosts and add them again after a server restart.
vcenter is the VCA version 5.5, 2646482