new R user struggling with error and convergence issues

Jennifer Yourkavitch via R-sig-mixed-models <r-sig-mixed-models at ...> writes:

Follow-up: glmmPQL works like a charm. I don?t really
 understand the difference between the algorithms
used by glmmPQL and glmer. Should I be concerned that 
the models ran with glmmPQL but not glmer?
Thanks,
Jennifer

The main case where Laplace approximation (the default glmer
algorithm) is significantly better than PQL is when there are a
small number of values per group; PQL depends more strongly than
Laplace approximation on the approximate Normality of the sampling
distributions of the conditional modes (predictions of the random
effects for particular groups).
   Do the predicted values make sense?

  Ben Bolker