COMPTEL Orion results revisited

COMPTEL observations of the Orion/Monoceros region have shown distinct evid ence for excessive 3-7 MeV emission which was attributed to nuclear deexcit ation lines from accelerated C-12 and O-16 nuclei. We must unfortunately co nclude now, however, that this appears to be a spurious result. This conclu sion follows from a better understanding of the instrumental background, fr om a better exposure of the region, and from an improved analysis method. W e show here how the impact of each of these gradually reduces the signal to a < 3 sigma result. The prime underlying cause seems to be Na-24 activatio n in and around the upper COMPTEL detectors, but we do not yet fully unders tand how this leads to the specific artifacts in our maps. As the influence of Na-24 is limited to about 2.5 to 4.5 MeV, mainly our Orion result can b e critically affected. Combining all available data, we must now set a 2 si gma flux upper limit on the 3-7 MeV emission of Orion of 3X10(-5) gamma cm( -2) s(-1), to be compared to a previously derived flux of similar to 10(-4) gamma cm(-2) s(-1).