[BioC] installing packages from CRAN problem

[Song, Guangchun]

When I try to install packages from CRAN under the menu of Packages, it
always gives me the following messages: 

> {a <- CRAN.packages()
+ install.packages(select.list(a[,1],,TRUE), .libPaths()[1], available=a)}

trying URL `http://cran.r-project.org/bin/windows/contrib/PACKAGES'
unable to connect to 'cran.r-project.org'.
Error in download.file(url = paste(contriburl, "PACKAGES", sep = "/"),  : 
        cannot open URL
`http://cran.r-project.org/bin/windows/contrib/PACKAGES'

What's wrong?

Thanks.


Guangchun