New CMB constraints on the cosmic matter budget: trouble for nucleosynthesis?

We compute the joint constraints on ten cosmological parameters from the latest CMB measurements. The lack of a significant second acoustic peak in the latest Boomerang and Maxima data favors models with more baryons than Big Bang nucleosynthesis predicts, almost independently of what prior information is included. The simplest flat inflation models with purely scalar scale-invariant fluctuations prefer a baryon density 0.022 <h^2 Omega_b < 0.040 and a total nonbaryonic (hot + cold) dark matter density 0.14 < h^2 Omega_dm < 0.32 at 95% confidence, and allow reionization no earlier than z~30.