http://sourceforge.net/tracker/index.php?func=detail&aid=1604261&group_id=235&atid=300235
If the network connection on a machine is changed while gaim is running, it
won't pick up the changes unless NetworkManager support is enabled. This
makes it always re-read the DNS info before a server connect.

This implemention is considered to be disliked because it re-reads the config files a few times
upon every connection.  There appears however to be no work underway to fix it properly.  This 
behavior is at least harmless while fixing the bug, so we will keep this patch for now.

diff -urN pidgin-2.0.0beta7devel.orig/libpurple/connection.c pidgin-2.0.0beta7devel/libpurple/connection.c
--- pidgin-2.0.0beta7devel.orig/libpurple/connection.c	2007-03-20 01:59:41.000000000 -0400
+++ pidgin-2.0.0beta7devel/libpurple/connection.c	2007-04-16 13:54:40.000000000 -0400
@@ -37,6 +37,10 @@
 #include "signals.h"
 #include "util.h"
 
+#include <netinet/in.h>
+#include <arpa/nameser.h>
+#include <resolv.h>
+
 static GList *connections = NULL;
 static GList *connections_connecting = NULL;
 static PurpleConnectionUiOps *connection_ui_ops = NULL;
@@ -139,6 +143,9 @@
 
 	purple_signal_emit(purple_connections_get_handle(), "signing-on", gc);
 
+	/* Re-read resolv.conf and friends in case DNS servers have changed */
+	res_init();
+
 	if (regist)
 	{
 		purple_debug_info("connection", "Registering.  gc = %p\n", gc);
diff -urN pidgin-2.0.0beta7devel.orig/libpurple/network.c pidgin-2.0.0beta7devel/libpurple/network.c
--- pidgin-2.0.0beta7devel.orig/libpurple/network.c	2007-04-01 11:51:46.000000000 -0400
+++ pidgin-2.0.0beta7devel/libpurple/network.c	2007-04-16 13:55:08.000000000 -0400
@@ -612,8 +612,6 @@
 	switch(current)
 	{
 	case LIBNM_ACTIVE_NETWORK_CONNECTION:
-		/* Call res_init in case DNS servers have changed */
-		res_init();
 		if (ui_ops != NULL && ui_ops->network_connected != NULL)
 			ui_ops->network_connected();
 		prev = current;