robust regression

Hi,

trying to do a robudt regression of a two-way linear model, I keep 
getting the following error:

 > lqs(obs ~ y + s -1,method="lms", contrasts=list(s=("contr.sum")))
Error: lqs failed: all the samples were singular

Robust regression with M-estimators works (also regular least square 
fits, of course):
rlm.formula(formula = obs ~ y + s - 1, method = "M", contrasts = list(s 
= ("contr.sum")))

I tried an exact sampling (psamp="exact"), but I keep getting syntax 
errors. Any idea how I can make the first one work?

Thanks,

joerg

----------------------------------------------------------
J?rg Schaber
Instituto Cavanilles de Biodiversidad y Biologia Evolutiva
Universidad de Valencia               Tel.: ++34 96 354 3666
A.C. 22085                            Fax.: ++34 96 354 3670
46071 Valencia, Espa?a                email : jos at uv.es