log axis error

Hi,
When trying to benerate a barplot with a log y axis from a data matrix I get an
error which I just cant figure out:

barplot(col.groups,beside=T,log="y")

Error in plot.window(xlim, ylim, log = "", ...) :
        formal argument "log" matched by multiple actual arguments

Can anyone tell me what this error means and possible solutions
Cheers, Jeremy