I would like to thank everyone in this thread for helping me solve my trouble. First the OP, Sutex, for coming back everytime he said he was giving up, thanks ! But especially the mods and people who relentlessly came here to help a sometimes snapish OP. I had the same problem, FOSE starting fine outside of MO. For the record, I'm not too sure of what I did, but in my case it seems that I had some BSAs in Archives that, unchecked, caused the problem. They were MenuVoices.bsa, Meshes.bsa, Misc, Sounds and Textures and Voices.bsa. Thanks Internet people!