[Admins]

That message about "Graal execution file is corrupted" is displayed when the checksum of the exe is wrong, probably Windows tries to insert something into the exe, which Graal doesn't allow.
It also checks at runtime if programs try to modify the Graal.exe memory, that might be the reason for the disappearing problem, would need to test it myself on a 64 bit Windows though to be able to fix it.