Sabre was removed from CRAN because certain bugs haven't been fixed by the authors and it doesn't seem to be maintained any longer. Perhaps you could switch to another package, fsay, lme4? What kind of models do you want to fit?

Thanks Dr. Daniel,

I want to fit a bivariate Poisson Mixed Model. can lme4 fit bivariate models?

TIA

The basis for mixed model analysis in lme4 is a model formula of the type Y~ x+(1|z) with the function glmer you can specify the family (gaussian, binomial, poisson) so lme4 can fit bivariate models.

Nope

I'm not familiar with bivariate Poisson regression, however, the MCMCglmm package might offer what you're looking for.