R packages need to be re-installed in the new version 3.0.0. R-Forge is in the process of uploading new versions, but in the meantime some packages fail to install (there is no compatible installation candidate). Obviously this post will be outdated in due time, but until then, it is quite easy to install R packages from the source:
(1) Navigate to the relevant page on R-Forge (you’ll probably land on the summary page, and have to click on R Packages on the top right)
(2) Download the source file (the .tar.gz next to the stylized penguin). Currently the files for Windows and Mac are unavailable.
(3) Open R, set the working directory to the downloaded file
install.packages("abc_0.1.tar.gz", repos=NULL, type="source"); with
repos=NULL indicating that a local file is used rather than CRAN, and
abc_0.1.tar.gz the exact name of the file.