POSTERIOR KERNEL OPTIMIZATION PROBLEM!
 (minus) the hessian matrix at the “mode” is not positive definite!*
=> posterior variance of the estimated parameters are not positive.
You should try to change the initial values of the parameters using
the estimated_params_init block, or use another optimization routine.
*Warning: The results below are most likely wrong! *
> In dynare_estimation_1 (line 315)
 In dynare_estimation (line 105)*
 In romer_estim_old.driver (line 247)*
 In dynare (line 293) *
MODE CHECK
Fval obtained by the minimization routine (minus the posterior/likelihood)): 13.409097
Warning: Matrix is singular, close to singular or badly scaled. Results may be
*inaccurate. RCOND = NaN. *
> In dynare_estimation_1 (line 338)
 In dynare_estimation (line 105)*
 In romer_estim_old.driver (line 247)*
 In dynare (line 293)*
Log data density [Laplace approximation] is NaN.
Error using chol
Matrix must be positive definite.
Error in posterior_sampler_initialization (line 84)
d = chol(vv);
Error in posterior_sampler (line 60)
 posterior_sampler_initialization(TargetFun, xparam1, vv,*
 mh_bounds,dataset_,dataset_info,options_,M_,estim_params_,bayestopt_,oo_);*
Error in dynare_estimation_1 (line 465)

posterior_sampler(objective_function,posterior_sampler_options.proposal_distribution,xparam1,posterior_sampler_options,bounds,dataset_,dataset_info,options_,M_,estim_params_,bayestopt_,oo_);*
Error in dynare_estimation (line 105)
 dynare_estimation_1(var_list,dname);*
Error in romer_estim_old.driver (line 247)
oo_recursive_=dynare_estimation(var_list_);
Error in dynare (line 293)
evalin(‘base’,[fname ‘.driver’]) ;
I’m trying to estimate the model with more than one observable variables (y_obs and c_obs)  when i estimate with only y_obs i receive no error messages so i think it could be in the definition of the additional shock variable/equation where it goes wrong.
Thanks!