Thanks for all the info. I've reluctantly moved the hdd to the primary onboard IDE controller of my B/W G3 (the original edition, the one with the very buggy CMD controller), and installation worked like a charm from then on. I still want to move the hdd back to the faster AEC controller, but getting all kinds of software to work properly on this system is currently more important than getting the speed up a bit. Anyway, it is already fast enough for now. I'll probably get around to setting up a new kernel sooner or later.
Jeroen PS: What is it with these buggy IDE controllers from CMD (now Silicon Image)? I have an ancient Dual Pentium 133 with a bad CMD640, and now a not so ancient Mac G3 B/W with a buggy CMD646, both built in! I also use a CMD649 on a more recent system, by the way, on a PCI add- on card, running faultlessly.
