pb with plot in nlme

hello all, 
I've got problems with plotting in nlme :

example(nlme)
plot(fm1)

Error in do.call(plotFun, as.list(args)) : 
	couldn't find function "xyplot"

I've seen in Changelog that there have been changes in plotting
funtions, may I've missed something...

nlme3.1-10 
         _                   
platform sparc-sun-solaris2.8
arch     sparc               
os       solaris2.8          
system   sparc, solaris2.8   
status                       
major    1                   
minor    2.2                 
year     2001                
month    02                  
day      26                  
language R

Mathieu Ros
DEA Math?matiques Appliqu?es
INRA-Toulouse

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