This is just the part where the kernel should be loaded, and start to execute.
I'm guessing that NetBSD tries to open a screenmode that you cant display. Do you have a gfx card on your machine?
One of the switches in the boot prompt, indicates whether it should open a dblpal or not screen, IIRC.
On the other hand, if you dont hear any hard disk activity, it could be something totally diferent.
Check with the NetBSD Amiga mailing list.
