[R] An lme model that works in old R.2.1.1 but not always in R.2.2.0 - why?

[Niels A. Sommer]

Following lme model runs fine in general under R.2.1.1 but only for 9 out
of my 11 response variables under R.2.2.0.

model for one of my response variables:
lme(Yresp~F1fix,random=list(const=pdBlocked(list(~F2mix-1,~Ass:F1fix-1,~F3mix-1,~F1fix:F3mix-1,~F2mix:F3mix-1),pdClass="pdIdent")))

Yresp is my response variable, F1fix is a fixed effect factor whereas
F2mix and F3mix are random effect factors.
const is set to rep(1,dim(Ycont)[1]).

The strange thing is that if an intercept is omitted (F1fix-1) the R.2.2.0
also runs a 100 %. It's the same model, just with another
parameterization??????

Niels Sommer