Default [Q] NAND Write Start Fail in Odin

Hi all,

for the last three days I've been carrying around a paper weight that looks remarkably like my Galaxy S3...
Anyway, I'm at a point where I don't know what else I could (or should) try. Today I thought I had a winner when I came across this thread:
I thought wrong. Flashing the bootchains works but then when I try flashing the root66.tar in Odin it always fails during NAND Write Start. I have seen people in the above thread with the same problem and then "never mind, I fixed it"-posts without explanations what they actually did... So, if you managed to fix it or know how to fix it, how does it work?
(I can't post in the same thread because I have less than 10 posts..)

Any input would be highly appreciated!

Thanks a lot and happy new year!