Well, i tried downgrading with these software updates:3.73 , 3.72 , 3.68 and 3.65 ,but no response.
I think that if i buy a SD2VITA reader and put the PSVITA card in the PC,and change the update file from 3.65 to 3.73 , it might work. I downgraded my PSVITA with ENSO, i think.
I will send you...