Alex, have you tried going back to using the stock Lucid version of the slapd binary (but with the /etc/defaults/slapd ulimit changes)?
(The very last comment on Debian bug 378261 seems to indicate that the -DOPENLDAP_FD_SETSIZE=8192 patch shouldn't actually make any difference in the Lucid version.)
Alex, have you tried going back to using the stock Lucid version of the slapd binary (but with the /etc/defaults/slapd ulimit changes)?
(The very last comment on Debian bug 378261 seems to indicate that the -DOPENLDAP_ FD_SETSIZE= 8192 patch shouldn't actually make any difference in the Lucid version.)