R help - Feb 2011 - glht{multcomp} : use with lme {nlme}

Hi dears,

I do
> CHOL<-lme(chol~rt*cd4+sex+age+rf+nadir+pharmac+factor(hcv)+factor(hbs)+
haartd+hivdur+factor(arv),
 random= ~rt|id, na.action=na.omit)

...runs sweet,..then

....try a multicomparisons approach for the categorical rf
> summary(glht(CHOL, linfct=mcp(rf="Tukey")))
*
Error in model.frame.default(object, data, xlev = xlev) :
  l'oggetto non è una matrice     *
<-- Object isn't a matrix!!*
Errore in factor_contrasts(model) :
  no ‘model.matrix’ method for ‘model’ found!
Errore in summary(glht(CHOL, linfct = mcp(rf = "Tukey"))) :
  error in evaluating the argument 'object' in selecting a method for
function 'summary'*


data are ok...I have followed the examples on ?glht ..,there is still
something I'm missing here?

Thanks  in advance if you wish to give a tiny answer.
-- 
*Little u can do against ignorance,....it will always disarm u:
is the 2nd principle of thermodinamics made manifest, ...entropy in
expansion.**....But setting order is the real quest 4 truth, ......and the
mission of a (temporally) wise dude.
*

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