R help - Mar 1999 - PCA centered

I tried make a pca analysis with R. For this propose i need centered rows and
columns. I make this using the function princomp:
> zz<-princomp(x,cor=TRUE)
When i do it each column have mean=0 and standard deviation=1.

But i have this problem: the total inertia, sum of Eigenval., dont is = 
                   =number of columns * 1= sum of total standard deviation

Why? It's a bug in R?

I have make  online this analyse in 
http://pbil.univ-lyon1.fr/ADE-4/ADE-4F.html
and everything it's OK.

Thanks in advance
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