error with glmer

Hi Hank,
I hope to be more clear now.

I am testing the influence of some dental restoration materials
Data, which are positively skewed and clustered, fit the assumption of 
being gamma distributed.

I tried glmer()
 >mod.glmer=glmer(mis~X_Igruppo_2+X_Igruppo_3+X_Igruppo_4+(1|mon),data=p4,family=Gamma(link='log'))

However,
 >summary(mod.glmer)
gives me back the following error message:
Error in asMethod(object) : matrix is not symmetric [1,2]

The same happens when I use lmer() with gamma family. It seems both 
glmer() and lmer() don't work when using gamma family. Did someone else 
experience this problem?

 >sessionInfo()
R version 2.7.2 (2008-08-25)
i386-pc-mingw32

locale:
LC_COLLATE=Italian_Italy.1252;LC_CTYPE=Italian_Italy.1252;LC_MONETARY=Italian_Italy.1252;LC_NUMERIC=C;LC_TIME=Italian_Italy.1252

attached base packages:
[1] stats     graphics  grDevices datasets  tcltk     utils     
methods   base    

other attached packages:
[1] lme4_0.999375-20   Matrix_0.999375-10 lattice_0.17-13    
xlsReadWrite_1.3.2 svSocket_0.9-42    svMisc_0.9-5       
TinnR_1.0.2        R2HTML_1.59      
[9] Hmisc_3.4-3      

loaded via a namespace (and not attached):
[1] cluster_1.11.11 grid_2.7.2      tools_2.7.2  

 > traceback()
15: .Call(dense_to_symmetric, from, "U", TRUE)
14: asMethod(object)
13: as(from, "symmetricMatrix")
12: .class1(object)
11: as(as(from, "symmetricMatrix"), "dMatrix")
10: .class1(object)
9: as(as(as(from, "symmetricMatrix"), "dMatrix"), "denseMatrix")
8: .class1(object)
7: as(as(as(as(from, "symmetricMatrix"), "dMatrix"), "denseMatrix"),
       "dpoMatrix")
6: asMethod(object)
5: as(sigma(object)^2 * chol2inv(object at RX, size = object at dims["p"]),
       "dpoMatrix")
4: vcov(object)
3: vcov(object)
2: summary(mod.glmer)
1: summary(mod.glmer)

error with glmer

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