[R] what does this warnings mean? and what should I do?

[ronggui]

I use lmer to fit a mixed effect model.It give some warnings.what does this warnings mean? and what should I do?

> (fm2.mlm <- lmer(qd ~ edu + jiankang + peixun +hunyin + cadcj + age + age2 + sex + dangyuan + Comp.1 + Comp.2+trust.cz1 +(trust.cz1|commid), data = individual,na.action = "na.exclude",family="quasibinomial")) 
Generalized linear mixed model fit using PQL 
Formula: qd ~ edu + jiankang + peixun + hunyin + cadcj + age + age2 +      sex + dangyuan + Comp.1 + Comp.2 + trust.cz1 + (trust.cz1 |      commid) 
   Data: individual 
 Family: quasibinomial(logit link)
      AIC      BIC    logLik deviance
 736.7059 821.8267 -349.3529 698.7059
Random effects:
 Groups   Name        Variance Std.Dev. Corr  
 commid   (Intercept) 1.56413  1.25065        
          trust.cz1   0.17922  0.42334  1.000 
 Residual             0.89728  0.94725        
# of obs: 652, groups: commid, 39

Fixed effects:
                  Estimate  Std. Error  DF t value Pr(>|t|)  
(Intercept)    -1.6115e-01  6.7997e-01 637 -0.2370  0.81274  
edu            -5.2585e-02  4.1048e-02 637 -1.2810  0.20064  
jiankang       -9.8243e-01  4.4645e-01 637 -2.2005  0.02813 *
peixun         -4.6307e-01  2.6397e-01 637 -1.7542  0.07988 .
hunyin         -1.2255e-02  2.8151e-01 637 -0.0435  0.96529  
hunyin         -2.7726e-01  1.3846e+00 637 -0.2002  0.84136  
hunyin         -2.9759e-01  8.7180e-01 637 -0.3414  0.73295  
cadcj           2.2366e-01  7.6467e-01 637  0.2925  0.77000  
age             9.3626e-02  4.0390e-02 637  2.3180  0.02076 *
age2           -1.3095e-03  5.5104e-04 637 -2.3763  0.01778 *
sex             3.9188e-01  1.9759e-01 637  1.9833  0.04776 *
dangyuan       -5.2558e-01  5.9091e-01 637 -0.8894  0.37410  
Comp.1          5.2463e-02  1.0309e-01 637  0.5089  0.61100  
Comp.2         -1.5048e-01  1.1435e-01 637 -1.3160  0.18863  
trust.cz1      -8.0709e-01  4.4632e-01 637 -1.8083  0.07103 .
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 
There were 11 warnings (use warnings() to see them)
> warnings()
Warning messages:
1: optim or nlminb returned message false convergence (8) 
 in: LMEopt(x = mer, value = cv) 
2: optim or nlminb returned message false convergence (8) 
 in: LMEopt(x = mer, value = cv) 
3: optim or nlminb returned message false convergence (8) 
 in: LMEopt(x = mer, value = cv) 
4: optim or nlminb returned message false convergence (8) 
 in: LMEopt(x = mer, value = cv) 
5: optim or nlminb returned message false convergence (8) 
 in: LMEopt(x = mer, value = cv) 
6: optim or nlminb returned message false convergence (8) 
 in: LMEopt(x = mer, value = cv) 
7: optim or nlminb returned message false convergence (8) 
 in: LMEopt(x = mer, value = cv) 
8: optim or nlminb returned message false convergence (8) 
 in: LMEopt(x = mer, value = cv) 
9: optim or nlminb returned message singular convergence (7) 
 in: LMEopt(x = mer, value = cv) 
10: optim or nlminb returned message singular convergence (7) 
 in: LMEopt(x = mer, value = cv) 
11: optim or nlminb returned message singular convergence (7) 
 in: LMEopt(x = mer, value = cv) 

> version
         _              
platform i386-pc-mingw32
arch     i386           
os       mingw32        
system   i386, mingw32  
status                  
major    2              
minor    2.0            
year     2005           
month    10             
day      06             
svn rev  35749          
language R     	



 				


2005-12-14

------
Deparment of Sociology
Fudan University

My new mail addres is ronggui.huang at gmail.com
Blog:http://sociology.yculblog.com