Make sure you have sd:\bootmii_ios.bin and sd:\cboot2_cios.bin sd:\bootmii
Casper is a program that will load mini code, like bootmii and cboot2 dol loader. It is an elf file that can be loaded via loader or exploit. There are 3 versions of it found here- Casper
In its default setup it loads sd:\bootmii_ios.bin, this is the armboot.bin from bootmii. Cboot2 casper is just hex edit to load sd:\cboot2_cios.bin.
To the point, you must get casper to load, which you have done, and you must get it to load sd:\bootmii_ios.bin which you have not done. You may wish to experiment with the other versions of casper to see if perhaps they will load bootmii for you.
This should work, it is most likely an issue with your sd card, or just picky picky software. But you must get it to work, no need to try anything else as casper loading cboot2 is the only way your going to hack this wii.