  We calculate at two-loop order in chiral perturbation theory the
electromagnetic corrections to the two-pion exchange nucleon-nucleon
interaction that is generated by the isovector spin-flip $\pi\pi NN$
contact-vertex proportional to the large low-energy constant $c_4\simeq 3.4
$GeV$^{-1}$. We find that the respective $2\pi\gamma$-exchange potentials
contain sizeable isospin-breaking components which reach up to -4% of
corresponding isovector $2\pi$-exchange potentials. The typical values of these
novel charge-independence breaking spin-spin and tensor potentials are $-0.11
$MeV and $0.09 $MeV, at a nucleon distance of $r=m_\pi^{-1}=1.4 $fm. The
charge-symmetry breaking spin-spin and tensor potentials come out a factor of
2.4 smaller. Our analytical results for these presumably dominant
isospin-violating spin-spin and tensor NN-forces are in a form such that they
can be easily implemented into phase-shift analyses and few-body calculations.
