R help - Jul 2003 - Memory explosion, plotting nmle grouped data object

Hi
I am using R 1.7.1 on RH linux 9.0 
> sum(unlist(lapply(ls(),function(x)object.size(get(x)))))/1024^2
[1] 2.424263

so I am not using much memory (I have a gig of ram on my machine)
now in nlme
>
gtest<-groupedData(log(X8)~Time|sub,all[,c(names(all)[1:9],"X8")],outer=~A*B)
> object.size(gtest)/1024
[1] 59.98438
> plot(gtest,outer=~Dose*chem,key=FALSE,asp=.5)
Plotting takes forever and from top while it is running

5663 wf00223   15   0 1151M 546M  1780 R     6.1 54.2   3:19   0 R.bin

Any Ideas why R is using so much memory?

Thanks
Nicholas