Wow. Shame to hear that it might have something to do with another system (the eclipse). I'm only offering this since I'm researching a Trans. Failsafe error on mine right now, but here's another link I thought was interesting-
http://www.xoutpost.com/x5-e53-forum/...light=failsafe

Such a small thing might also explain it being missed on diagnostics (found 20 threads about this when I searched, and few if any were solved/fingered by dealer diagnostics). If that link doesn't match your situation, I'd recommend a search since there are tons of tips in the archives.
I'm 'in the trenches' with you apparently on this transmission error!