I am not yet banned, however, my gamertag has been banned before.
Originally I had v1.1 xbox with an X2 lite chip in it. I logged onto live once when i was drunk with the modchip banned, needless to say, I got banned.
After that I purchased a new Xbox (v1.4), and moved my same gamertag from the original Xbox to this new one. The newer Xbox IS modified with an X2.6. It was not modified until after it had already been on live for several months. I just recently modified it. I have played Halo 2 multiple times a day since its release, and have not been banned. I have the original HD in the Xbox, with the F: created. I have no other dashes on my C: besides the MS dash. I unplug the ethernet from the back every time I am about to turn the mod chip on, and have yet to have any problems.
If you have any other questions, let me know. I hope this helps someone figure out what MS is doing.