I have now tried two Wii's, both I have hard modded with the original Wiikey modchip version 1.99 firmware, wondering if this has ANYTHING to do with it. Do you have hardmod, or softmod?
I was wondering at first if me having dsmios lite installed first may have caused the black screens for me, but I then tried my other Wii and it hasn't had any new IOS's installed in sometime, I had to install all the DX2 v8 wads (with wadman) and dios mios 2.0 v4 and all I get with dml booter is black screen on it and on my SD cards. I find it hard to believe it is how I have my drive setup as I get the same results with SD card (dml booter lets you select sd or usb.)
Can we at least try to validate if people with hard chipped Wii's are getting this to work??? If so, what chip and version bios on that chip? This sounds like the only possible for me right now as I have completely cleaned a Wii to version 4.0u, installed only ios58, 249, d2x v8 and dios mios 2.0 and still no luck, same black screen.
----update on 07/08/2012
All seems to be working now, turns out it was my USB controller for the HDD. I tried two of them without success and the one I rx'd earlier today is running fine..