R help - Jul 2006 - Warning message

Dear reader,

I am trying to simulate 1000 data from nonlinear model in order to be able to
do
mixed effect analysis. If the program works but give you following warning
message, what should I do? Can I still accept the result, which is about the
precision of model parameter estimation? 


FALSE CONVERGENCE. in: ms( ~  - logLik(nlmeSt, nlmePars), start = list(nlmePars
	c(coef(nlmeSt))), control =  ....
SINGULAR CONVERGENCE. in: ms( ~  - logLik(nlmeSt, nlmePars), start list(nlmePars
c(coef(nlmeSt))), control =  ....


Thanks

Farinaz