afni.nimh.nih.gov

If you're on a Mac, there seems to have some issue with the most recent version (v1.13.0) of data.table:

[rdrr.io]

To get around the problem (before the package maintainer fixes the problem in the next version release), install an older version of data.table:

1) Download the older version from here to a temporal directory:
[cran.r-project.org]

2) At the terminal, execute the following command:
R CMD install data.table_1.12.8.tgz

3) Try your 3dLME script and see if it works.

Gang