I tried to purchase a couple monsters from Vivi for her Experimentation area, but I think that whole piece might be bugged in v0.45. I don't know if maybe it's because I used a save from v0.44a, but when the window opens up to select a monster, only the slider bar seems to be working. I can't select or even highlight any of the mobs. When I exit the window, there's an empty dialogue box that only seems to go away when I talk to someone else who has a shop window of some kind.
Like Vivi's nurse assistant or whatever she is in the front room. If I talk to that cunt and choose the cancel option instead of shopping, it brings up Vivi's monster window again, which is still otherwise unresponsive, and when closing that window, the blank dialogue box remains. If I choose shopping instead, it brings up the proper window with the red potions and they can be bought as normal. When I close that window, the blank dialogue box goes away.