When I update my R4, it won't work?

Okay, I have an r4 III revolution and have tried to update it by following basic procedures (downloading new kernel, copying files onto micro sd card) but when I put it in my DS it just has a black screen saying "loading..." and doesn't load, so I have to plug it back into my computer and put my old files back on it. I have tried different kernel files (v.1.18, v.1.17, etc.) but none work and I don't want to have to buy a new r4