You were right.
I found by using the Verify option in DiskUtil that here are some error on my system disk.
Nevertheless, the error was reported at the end of the virtual disk, just in the very end.
So I used dd like this
dd if=mybad.vmdk of=/Volumes/External/copy.vmdk conv=noerror,sync count=162000000
(i did some calculations on how many block my SCSI disk have).
Guess what? I was able to open a new VM with this image, wih some very few dll lost or corruote but all my that is there.
Best regards