How do I assign different spells or spell levels to different number keys? The game tells me to hold down the according number key while clicking OK, but as long as I keep a number key pressed, I can't move or click the mouse at all ...

i just went in and played around with it
it seems that to assign hotkey you need to use the normal number keys not the number pad keys
though you can use the pad keys for selecting them later once set

happy casting fellow gog'sperson