The uploaded upgrade package cannot be used with VMware vSphere Update Manager

Hello,

I am ugrading a vmware system (Vcenter + 3 host)  from 5.1 to 5.5

I did a total reinstallation of Vcenter and Update manager in 5.5 version, using a new database.

Then, I want to update my hosts with Update Manager.

When I upload VMware-VMvisor-Installer-5.5.0-1331820.x86_64 into Update Manager, I get the message : The uploaded upgrade package cannot be used with VMware vSphere Update Manager

I also tryed to import VMware-VMvisor-Installer-5.1 (Build: 1065491) but I get the same error

To my mind, the vmware KB2009812 isn't applicable, because I updated UDM first in 5.5

Any idea??

thx a lot