That's because I installed a slighty newer version of 2.1 on your system. That includes the easy inclusion for the support of overlib (the brewt and nessa templates only).
The files which have been changed to include the overlib support are (see the brewt or nessa templates for these changes):
globals.txt
home.htm
msgs_list.htm
msgs_list_include.htm
msgs_search_results.htm
msgs_threaded_include.htm
If you want a more detailed diff, I can do that too, but I'm not in the office yet .
Adrian