PCA - princomp can only be used with more units than variables

Hi all:
I am trying to do PCA on the following matrix. 


            N1     N2    A1      A2     B1     B2
gene_a      90    110    190    210    290    310
gene_b     190    210    390    410    590    610
gene_c      90    110    110     90    120     80
gene_d     200    100    400     90    600    200

dataf<-read.table("matrix")

pca<-princomp(dataf,cor=TRUE,scores=TRUE)

Error in princomp.default(dataf, cor = TRUE, scores =
TRUE) : 
        princomp can only be used with more units than
variables


Can any one help me, whats wrong here. 

thanks
srini