I've been working on my v4, trying to get to a point where I can qnxflash it. Made it through most steps pretty well: custom c/h/s setting; wrote iop_v2_sandisk_dump to it; put it in the io and got it to boot up in the tutorial. So far so good.
I then followed acer123 and thepublic's instructions to change various nvram settings in an attempt to connect to my isp. Dialing and connect worked fine, but the route never seemed to come up. I rebooted a few times and the tutorial didn't come up again. A screen saying "...updating..." came up, but I could still tab-444 to the root window. So that was still workable.
At some point, though, this changed. Now, it boots right into the regular user screen and I can't tab-444 to the root prompt. I've even taken the drive out, re-fdisk'd it, and re-dd'd the iop_v2 image. Since this put me in the tutorial the first time I figured it would work again. Nope.
So, to summarize, I can't seem to get to the root window by any means anymore, whether it's booting form the sandisk or from the v2 image disk.
I suspect it has something to do with the stuff I wrote to nvram having to do with the shadow file...