[r] Unable to install packages in latest version of RStudio and R Version.3.1.1

As @Pascal said, it is likely that you encounter problem with the firewall or/and proxy issue. As a first step, go through FAQ on the CRAN web page. After that, try to flag R with --internet2.

Sometimes it could be useful to check global options in R studio and uncheck "Use Internet Explorer library/proxy for HTTP". Tools -> Global Options -> Packages and unchecking the "Use Internet Explorer library/proxy for HTTP" option.

Hope this helps.