This is about recent packages failing to load on Mac in R 2.4.1 with "unable to load shared library" errors: The good news is that I found and fixed the problem, the bad news is that the build machine is slow and needs to re-build both R and the packages which will take some time. Expect most fixed packages to be online sometime tomorrow from the R.research.att.com site and correspondingly later on the mirrors. (R 2.5.0 is not affected and I encourage you to test the RC so bugs can be fixed before the release!!) For those that missed the hot fix: install gcc4.0.3 from the full R 2.4.1 installation image if you want the problem to go away immediately without re-installing packages. (Open the R 2.4.1 full image from CRAN, double-click on "Packages" and then "gcc4.0.3") Cheers, Simon PS: I'm cross-posting this to R-devel, because people don't read the FAQ and don't look where they should - sorry about that.