Instructions:

cd BitchX/source
patch < /path/to/75p3-format.patch

It should apply cleanly.  Then recompile bx and restart your client.

--- parse.c.orig	Mon Jul  3 05:20:51 2000
+++ parse.c	Mon Jul  3 05:21:15 2000
@@ -1150,7 +1150,7 @@
 				else
 					bitchsay("Press %s to join %s", s, invite_channel);
 			}
-			logmsg(LOG_INVITE, from, 0, invite_channel);
+			logmsg(LOG_INVITE, from, 0, "%s", invite_channel);
 		}
 		if (!(chan = lookup_channel(invite_channel, from_server, 0)))
 			check_auto_join(from_server, from, invite_channel, ArgList[2]);
@@ -1211,7 +1211,7 @@
 			fudge_nickname(from_server, 1);
 		if (get_int_var(AUTO_RECONNECT_VAR))
 			servercmd (NULL, sc, empty_string, NULL);
-		logmsg(LOG_KILL, from, 0, ArgList[1]?ArgList[1]:"(No Reason)");
+		logmsg(LOG_KILL, from, 0, "%s", ArgList[1]?ArgList[1]:"(No Reason)");
 	}
 	update_all_status(current_window, NULL, 0);
 }