[R-sig-ME] warning error question

[Anahí Fernández]

hi!! I run this model in lme4:
"M.4=glm(Cuenta~carga*categ.asoc+(1|campo/foto)
          +offset(log(area.foto)),family=poisson(link =
"log"),data=tipocat)"
And I have this warning message: "Warning message:
In checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv,  :
  Model failed to converge with max|grad| = 0.00432818 (tol = 0.001,
component 1)"
I don´t know what is that means, could you help me, please!!
My datatable is attached...

Cheers, Anahí

-- 
Anahí R. Fernandez
Lab. Ecotono-INIBIOMA
CONICET- Univ. Nac. del Comahue
Quintral 1250 (8400), Bariloche, Argentina