R help - Dec 2007 - error message in lmer for logistic regression model with random intercept and slope

Greetings,

I am trying to run a logistic regression model for binary data with a random
intercept and slope in R 2.6.1.  When I use the code:

lmer1<-lmer(infect ~  time+gender + (1+time|id), family=binomial, data=ichs,
method="Laplace")

Then from:
 summary(lmer1)
I get the message:

Error in if (any(sd < 0)) return("'sd' slot has negative
entries") :
  missing value where TRUE/FALSE needed

The model with just a random intercept has no difficulty.  That is the model:

lmer1<-lmer(infect ~  time+gender + (1|id), family=binomial, data=ichs,
method="Laplace")

yields no such message.  Can someone please tell me what this is about and how
to remedy?

Thank you,
Margaret Gorlin
PhD Student
UMDNJ SPH

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