[R] unexpected "false convergence"

[Jack Tanner]

I've come into some code that produces different results under R 2.1.1 and R 
2.2.1. I'm really unfamiliar with the libraries in question (MASS and nlme), 
so I don't know if this is a bug in my code, or a regression in R. If it's a 
bug on my end, I'd appreciate any advice on potential causes and relevant 
documentation.

The code:

score<-c(1,8,1,3,4,4,2,5,3,6,0,3,1,5,0,5,1,11,1,2,4,5,2,4,1,6,1,2,8,16,5,16,3,15,3,12,4,9,2,4,1,8,2,6,4,11,2,9,3,17,2,6)
id<-rep(1:13,rep(4,13))
test<-gl(2,1,52,labels=c("pre","post"))
coder<-gl(2,2,52,labels=c("two","three"))
il<-data.frame(id,score,test,coder)
attach(il)
cs1<-corSymm(value=c(.396,.786,.718,.639,.665,.849),form=~1|id)
cs1<-Initialize(cs1,data=il)
run<-glmmPQL(score~test+coder, 
random=~1|id,family=poisson,data=il,correlation=cs1)

The output under R 2.2.1, which leaves the run object (last line of the 
code) undefined:

iteration 1
iteration 2
iteration 3
iteration 4
Error in lme.formula(fixed = zz ~ test + coder, random = ~1 | id, data = 
list( :
        false convergence (8)

Under R 2.1.1, I get exactly 4 iterations as well, but no "false 
convergence" message, and run is defined.