[Limdep Nlogit List] problem matrix singular in latent class model

[Elias José Gordillo Chávez]

Dear Willian Greene 
Thank you very much; I can run the model with my full dataset (876 individuals and three options). But I have a problem I can only run the model with two classes; if I try to use 3 or 4, I get an error message: Error 1027: Models - variance matrix of estimates is singular. 

My question is, is it possible that my data is inappropriate for the model, or am I specifying the model wrong? 

I used the following syntax for the random latent class:

LCRPLOGIT
;LHS=CHOICE
;CHOICES= A,B,C
;RH2=ONE
;RHS=LAND75,LAND25,LAND10,INTENS,SILVO,EXTENS,WP,JAG0,JAG2,JAG9
;RPL
;DRAWS=50
;FCN= LAND75(t),LAND25(t),LAND10(t),INTENS(t),SILVO(t),EXTENS(t),WP(t),JAG0(t),JAG2(t),JAG9(t)
;HALTON
;PDS=6
;PTS=2 
;maxit=100; tlg=.0001
;lcm
U(A)= LAND75*LAND75 + LAND25*LAND25 + LAND10*LAND10 +INTENS*INSTENS + SILVO*SILVO + EXTENS*EXTENS +WP*WP +JAG0*JAG0 +JAG2*JAG2+JAG9*JAG9/
U(B)= LAND75*LAND75 + LAND25*LAND25 + LAND10*LAND10 +INTENS*INSTENS + SILVO*SILVO + EXTENS*EXTENS +WP*WP +JAG0*JAG0 +JAG2*JAG2+JAG9*JAG9/
U(C)= LAND75*LAND75 + LAND25*LAND25 + LAND10*LAND10 +INTENS*INSTENS + SILVO*SILVO + EXTENS*EXTENS +WP*WP +JAG0*JAG0 +JAG2*JAG2+JAG9*JAG9$


Thank you
Regards 
Elias Gordillo 


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