On Thu, 31 Mar 2011, Mike Estrada wrote: Gretl can't find a well-defined maximum for the likelihood within the admissable parameter space. One point to note is that series to be analysed via GARCH should have a constant conditional mean -- they shouldn't be trending, after controlling for any included regressors. With exchange rates, which are likely to trend based on differential inflation rates, one would either include variables that account for the trend or perhaps run the analysis in first-differences of logs. Allin Cottrell