This seems like a connectivity issue, R is not being able to connect to the CRAN repository you have selected, these are some things to try.
Choose a different CRAN repository, RStudios repository is a good choice (http://cran.rstudio.com/) or you could choose one that is geographically closer to you.
Check if your internet connection has traffic restrictions of some kind, like a firewall, proxy server, etc. This is usually the case when you are at work or school.
Do you have any additional information that might be relevant? I'm afraid that without more information there is nothing else we can do for you, connectivity issues are system dependant and hardly related to the IDE.