Some warning messages

Hi All,

Sometimes I get one or two the following warning messages, when I fit my data using "lme4".
Could someone tell me whether or not are they crucial?
How could I fixed such problems?

Thank you very much.

1)
The following object(s) are masked from 'package:base':

    det


Attaching package: 'lme4'

The following object(s) are masked from 'package:stats':

    AIC, BIC


2)

Warning message:
In data != data[[1]] :
  longer object length is not a multiple of shorter object length

3)
Warning message:
In mer_finalize(ans) : singular convergence (7)

Likan