I wonder if maybe your DLM path is pointing to the wrong version of IDL? You can check this by entering the following command into the IDL terminal: print, !dlm_path If this path is pointing to the wrong location, a possible cause might be if you have an environment variable called IDL_DLM_PATH that is pointing to the wrong location. If this is the case, you should be able to remove this environment variable and it should fix the problem.