A new version of the data.table package was released by its maintainers to CRAN. This version should work with the current version of the photobiology packages. Users of my packages should update data.table. At the moment a binary package for OS X seems not to be available, until it becomes available, you will need to install from source on Mac computers, which requires instalation of Xcode and accepting its license. For Windows, binary is available from CRAN.