  We investigate the perturbative stability of a nonsupersymmetric D7 - anti-D7
brane embedding in a particular class of type IIB backgrounds. These
backgrounds are the gravitational duals of certain strongly-coupled gauge
theories, that exhibit a nearly conformal regime (known as a walking regime).
Previous studies in the literature have led to conflicting results as to
whether the spectrum of fluctuations around the flavor D7 - anti-D7 embedding
has a tachyonic mode or not. Here we reconsider the problem with a new
analytical method and recover the previously obtained numerical results. We
also point out that the earlier treatments relied on a coordinate system, in
which it was not possible to take into account fluctuations of the point of
confluence of the D7 - anti-D7 branes. Using an improved coordinate system, we
confirm the presence of a normalizable tachyonic mode in this model, in
agreement with the numerical calculations. Finally, we comment on the
possibility of turning on worldvolume flux to stabilize the probe branes
configuration.
