R help - Mar 2006 - warning message using lmer()?

Dear all,

I use lmer to fit a mixed effect model.It give some warnings. What can I 
do about this?

Here is the function and the warning message:
> model.growth.mcas5 <- lmer(response ~ monthElapsed + 
(monthElapsed|studentID),
+            data= mcas5, family=binomial(link="logit"),
method='ML')

Warning messages:
1: nlminb returned message false convergence (8)
  in: LMEopt(x = mer, value = cv)
2: nlminb returned message false convergence (8)
  in: LMEopt(x = mer, value = cv)
3: nlminb returned message false convergence (8)
  in: LMEopt(x = mer, value = cv)

I tried to increase maximum iteration limit  by adding
     control=list(msMaxIter=600, maxIter=300, PQLmaxIt=100)
That seems not help.


What can I do next?


Thanks all!



Mingyu Feng
===============================================================================Department
of Computer Science            Tutoring Research Group
Worcester Polytechnic Institute