Error message in dredge function (MuMIn package) used with binary GLM

Hi all,

I'm having trouble with the model generating 'dredge' function in the
MuMIn
'Multi-model Inference' package.

Here's the script:

globalmodel<- glm(TB~lat+protocol+tested+
streams+goats+hay+cattle+deer,
family="binomial")
chat<- deviance(globalmodel)/59 #There we 59 residual degrees of freedom
in
this global model.
models<- dredge(globalmodel, beta=FALSE, evaluate=TRUE, rank="AICc",
chat=chat, fixed=NULL, trace=FALSE)

And the error message is:

Error in UseMethod("logLik") :
  no applicable method for 'logLik' applied to an object of class
"logical"

I have trawled the literature and it seems to be ok to use a binary GLM as
the global model - could this be the problem? The variables are a mix of
binary and continuous data.

Any thoughts?
Thanks,
Cat