@Vincent
I had the same problem when I installed OS3.9 on my A2000 quite a while back, and I'll be darned if I can think of what solved the problem. Suffice to say that if I could figure it out, you sure can too, I know just enough about the Amiga to be dangerous to myself. Don't give up, and in the meantime, if I remember what the fix was, I'll let you know pronto.