Error in R CMD Check: Packages required but not available

It's working now.

What I did was:

1. add ~/R/x86_64-redhat-linux-gnu-library/2.15 to .libPaths (That's where my R library was)
2. Detach all libraries in R
3. Restart the R session. (For multiple sessions, close all of them.)
4. install the required packages.
5. Check if the Imports & Exports are correct in the namespace file.
6. Check if the required fields are available in the Description file. Make sure all dependencies are handled between 'Depends', 'Imports', 'Suggests' and 'Enhances'.
7. Checked it. R CMD check <pkg>. Built it. R CMD build <pkg>. Installed it. R CMD INSTALL <tarball>.
8. Done.