Weird timing, but I also had the exact same problem mentioned and fixed it the way Jarod mentioned. Details were: 1) FO3 could be launched outside of MO with and without FOSE. 2) FO3 would crash when launched directly from MO, and FOSE would finish launching but subsequently FO3 would be stuck permanently at a black screen prior to any loading image. 3) Once all of Jarod's listed BSAs were checked in the Archives tab, MO could launch FOSE normally. I re-read the STEP instructions and couldn't find anything mentioning a need to tick those BSAs to be managed by MO. Did I miss something, or is that normally not needed or desired?