  Similarities between fragile glasses and spin glasses (SG) suggest the study
of frustrated spin model to understand the complex dynamics of glasses above
the glass transition. We consider a frustrated spin model with Ising spins and
s-state Potts spins both with and without disorder. We study the two models by
Monte Carlo simulations in two dimensions. The Potts spins mimic orientational
degrees of freedom and the coupled frustrated Ising spins take into account for
frustrating effects like the geometrical hindrance. We show that in this model
dynamical transitions and crossovers are related to static transitions. In
particular, when disorder is present, as predicted and verified in SG, a
dynamical transition between high-temperatures exponential to low-temperatures
non-exponential correlation functions numerically coincides with the ordering
temperature of the ferromagnetic regions, i.e. the Griffiths temperature
$T_c(s)$, while a crossover between power law growth of correlation times to
Arrhenius law occurs near a Potts transition at $T_p(s)<T_c(s)$. In the model
without disorder, where $T_c(s)$ is not defined, both dynamical transition and
crossover occur at $T_p(s)$. Furthermore the static susceptibility and the
autocorrelation times of quantities depending on Potts spins diverge at
$T_p(s)$. This is reminescent of recent experimental results on glass-forming
liquids.
