Pacman 3.0.5-1 had a bit of an issue with permissions when installing packages that contained symlinks. A well-intentioned chmod call turned permissions on some files to 777 creating a security risk. This has been fixed in pacman 3.0.5-2.
More details: http://bugs.archlinux.org/task/7461 http://archlinux.org/pipermail/pacman-dev/2007-June/008579.html