Undefined R-structure MCMCglmm

Hi,
I am getting the following error when fitting a zip model in MCMCglmm.

 > fit1 <- MCMCglmm(sus ~ 1 + ethnic + sped + ell + risk + male + grade, 
random=~id.f, data=enroll.long.m, verbose=TRUE, DIC=TRUE, 
family="zipoisson") # Random intercept only model
Error in MCMCglmm(sus ~ 1 + ethnic + sped + ell + risk + male + grade,  :
   R-structure does not define unique residual for each data point

I was able to run fit a poisson model but my data is zero-inflated.

Thanks,
Chris

Christopher David Desjardins
Ph.D. Student
Quantitative Methods in Education
Department of Educational Psychology
University of  Minnesota
http://cddesjardins.wordpress.com/