Different versions of lme4 and covariance of random effects

All,

I recently re-estimated a model after upgrading to Rv2.7.1 that had been
estimated Rv2.6.2 previously and was surprised to see the estimated
correlation between random effects in the model change from 0.3 to 1.0.
It appears that the reason has more to do with the version of lme4 since
when I download the latest possible lme4 to Rv2.6.2 the results agree.

Below is a reproducible example where the difference in results is not as
dramatic.  Of course, for my data the initial results with the correlation
of .3 seem a lot more plausible than that of 1.0 so I'm inclined to trust
those results more than the newer ones.  It seems strange to get the
correlation of 1.  

Cheers,
David

library("lme4")
set.seed(500)
n.timepoints <- 4  ## change for shorter examples
n.subj.per.tx <- 20
sd.d <- 5;
sd.p <- 2;
sd.res <- 1.3
drug <- factor(rep(c("D", "P"), each = n.timepoints, times =
n.subj.per.tx))
drug.baseline <- rep( c(0,5), each=n.timepoints, times=n.subj.per.tx )
Patient <- rep(1:(n.subj.per.tx*2), each = n.timepoints)
Patient.baseline <- rep( rnorm( n.subj.per.tx*2, sd=c(sd.d, sd.p) ),
each=n.timepoints )
time <- factor(paste("Time-", rep(1:n.timepoints, n.subj.per.tx*2),
sep=""))
time.baseline <- rep(1:n.timepoints,n.subj.per.tx*2)*as.numeric(drug=="D")
dv <- rnorm( n.subj.per.tx*n.timepoints*2,
mean=time.baseline+Patient.baseline+drug.baseline, sd=sd.res )
dat.new <- data.frame(time, drug, dv, Patient)
dat.new$Patient.cross <- rep(1:(n.subj.per.tx), each = 2*n.timepoints)

dat.new$Dind <- as.numeric(dat.new$drug == "D")
dat.new$Pind <- as.numeric(dat.new$drug == "P")
dat.new$time.num = rep(1:n.timepoints, n.subj.per.tx*2)

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