  Recent improvements in stellar models for intermediate-mass and massive stars
are recalled, together with their expectations for the synthesis of radioactive
nuclei of lifetime $\tau \lesssim 25$ Myr, in order to re-examine the origins
of now extinct radioactivities, which were alive in the solar nebula. The
Galactic inheritance broadly explains most of them, especially if $r$-process
nuclei are produced by neutron star merging according to recent models.
Instead, $^{26}$Al, $^{41}$Ca, $^{135}$Cs and possibly $^{60}$Fe require
nucleosynthesis events close to the solar formation. We outline the persisting
difficulties to account for these nuclei by Intermediate Mass Stars (2
$\lesssim $ M/M$_\odot \lesssim 7 - 8$). Models of their final stages now
predict the ubiquitous formation of a $^{13}$C reservoir as a neutron capture
source; hence, even in presence of $^{26}$Al production from Deep Mixing or Hot
Bottom Burning, the ratio $^{26}$Al/$^{107}$Pd remains incompatible with
measured data, with a large excess in $^{107}$Pd. This is shown for two recent
approaches to Deep Mixing. Even a late contamination by a Massive Star meets
problems. In fact, inhomogeneous addition of Supernova debris predicts
non-measured excesses on stable isotopes. Revisions invoking specific low-mass
supernovae and/or the sequential contamination of the pre-solar molecular cloud
might be affected by similar problems, although our conclusions here are
weakened by our schematic approach to the addition of SN ejecta. The limited
parameter space remaining to be explored for solving this puzzle is discussed.
