Current rev. of sneek2o are suffering from a timing issue in the di module. Due to that, the system sometimes hangs on a black screen during boot.
This is only the case with sneek2o, and not with uneek2o.
Another known issue is that some sdhc aren't recognised properly if you use bootmii @ boot2 to launch into neek.
In that case, booting the wii with the sd card out, inserting the sd card, and launching bootmii from the homebrew channel or another homebrew application solves the issue.
Using the channel on the neek2o google svn is the preferred method to boot into neek2o.
If you enter the correct serial for your wii to create the settings.txt, your network should work with a modmii created nand.
In my case however, I can only accept the Eula and go to the shopping channel on a 4.2E modmii created nand.
If I create a 4.3E that way, It always fails when I try to go to the Eula screen.
So, if I understand correctly, you have a working nand, you hit the 1 button and the nand becomes corrupt? What version of neek2o are you using?