During the process, i cleaned up credentials.
And next day i add failed jobs with :
Removing proxies located on the host and reinstallling them corrected things.Error: Client error: NFC server [my_shiny_esxi_host is busy. Failed to retrieve next FILE_PUT message. File path: [[DataStore] myvm/myvm.vmx]. File pointer: [0]. File size: [3545].
I realised it had to be this when i saw that jobs performed with proxies other than those on the host worked.
In the process i made a comple new installation of vbr, with the 2008R2 64 bits sql database, so i've not wasted my time .