You made a smart move in trying a more well-known diagnostic utiltity, especially as Victoria is only "experimental" software and looks very crude judging by the screenshots on their website. Main reason you initially received no replies is the fact that very few THF members have used it because it's so primitive and clunky.
I see, thank you for your comment, Phillip.
In any case, I think that what's causing all the blocks is the fact that "something" keeps accessing the drives even when they're supposed to be idle. But that happens only when USB 3.0 drivers are enabled.
By the way, the drives look fine when I scan them on another computer.
I wonder if leaving the drives constantly connected to my "problematic" laptop will somehow damage them or prematurely wear them out (?). I think that if I could do a clean installation of Windows now, I would fix these problems. But I hope there's a less invasive and time consuming way... I tried reinstalling USB drivers, for instance, but it didn't work.