[R] R not responding for nested glm model

[Yuval Sapir]

Hi,
I'm trying to perform a glm model on count data (poisson distribution of 
the errors) where data are nested.
glmmodel<-glm(y~x/z,poisson)
x and z are factors, z nested within x, y is count data.
In that point the R just "stuck" and not respond anymore. I tried
glmmodel<-glm(y~x,poisson)
and there were no problems. Trying
glmmodel<-glm(y~x/z)
gave the same no response. Similar problem with continuous data (normal 
distribution of the errors).
I am using R 2.3.1 on Windows XP
Thanks
Yuval

-- 
Yuval Sapir, PhD
Post-doctorate research associate
Dept of Genetics
University of Georgia
Athens, GA 30602, USA