UPDATE 2:
Installed the 5.1 and the APD behaviour is the same as 5.1 U1 (blocking popup appears on Physical RDM APD).
I tried also the parameter
Misc.APDHandlingEnable = 0
wich eventually would to rever to the old behaviour (as far as i've understood) but the popup kicks-in again on RDM APD
Someone can shred some light on this?
Thank you very much
PS:
In poor word, to summarize i would need to disable the popup in order to make the VM keep working