Are you running LISTSERV HPO?  If not I can imagine plain LISTSERV Classic
taking a long time to add 100K users.  It doesn't look to me like you have
an HPO LAK, at least as far as I can tell from the records.

For a fairly graphic description of the difference, see

 http://www.lsoft.com/products/default.asp?item=listserv_perf

Nathan