Ok, I just installed VS on my MacBook Pro and it seems to run fine. Then I reinstalled it on my iMac and I deleted my game folder and created a new one. Now I can load the walking sequence. But I have problems setting the center of the animation, sometimes VS shows me the crosshair and allows me to set the center, sometimes it does nothing and just shows the default mouse cursor.
I could also load a background image and place a new scene object where Jacob would start in the image, but after doing so I could not save & run the game, it gave me some errors and an abnormal program termination. I'll try again tomorrow. I'll see if runs better on the MacBook, but I'd rather work on the iMac for the more comfy screen size. (Or will I have to buy a Windows PC in the end? Maybe I could use it as a step for reaching high shelves after finishing the game)