You can fit this kind of model (and negative binomial) and more
difficult mixed models with AD Model Builder's random effects module
which is now freely available at
http://admb-project.org/
--
David A. Fournier
P.O. Box 2040,
Sidney, B.C. V8l 3S3
Canada
Phone/FAX 250-655-3364
http://otter-rsch.com