8x faster modem connection using pon/poff vs. network-admin (gnome network settings)

[Jaime]

Hi.

I have a laptop with an external serial 56k modem which works perfectly
whenever I connect using pon/poff - I can download at rates between
8KB/s and 10KB/s. I've also set-up a connection, on the same machine
using the same modem to the same isp etc etc, using network-admin (gnome
network settings) and whenever I use this, the connection is much slower
- at best, I can download at 1KB/s - sometimes the connection locks up
completely.

Here's /var/log/messages from the (working) pon/poff session:
Apr 21 04:23:34 localhost pppd[8737]: pppd 2.4.2 started by root, uid 0
Apr 21 04:23:34 localhost pppd[8737]: Removed stale lock on ttyS0 (pid
8546)
Apr 21 04:23:35 localhost chat[8738]: abort on (BUSY)
Apr 21 04:23:35 localhost chat[8738]: abort on (NO CARRIER)
Apr 21 04:23:35 localhost chat[8738]: abort on (VOICE)
Apr 21 04:23:35 localhost chat[8738]: abort on (NO DIALTONE)
Apr 21 04:23:35 localhost chat[8738]: abort on (NO DIAL TONE)
Apr 21 04:23:35 localhost chat[8738]: abort on (NO ANSWER)
Apr 21 04:23:35 localhost chat[8738]: abort on (DELAYED)
Apr 21 04:23:35 localhost chat[8738]: send (ATZ^M)
Apr 21 04:23:35 localhost chat[8738]: expect (OK)
Apr 21 04:23:35 localhost chat[8738]: ATZ^M^M
Apr 21 04:23:35 localhost chat[8738]: OK
Apr 21 04:23:35 localhost chat[8738]:  -- got it
Apr 21 04:23:35 localhost chat[8738]: send (ATDTxxxxxxxxxxx^M)
Apr 21 04:23:36 localhost chat[8738]: expect (CONNECT)
Apr 21 04:23:36 localhost chat[8738]: ^M
Apr 21 04:23:57 localhost chat[8738]: ATDTxxxxxxxxxxx^M^M
Apr 21 04:23:57 localhost chat[8738]: CONNECT
Apr 21 04:23:57 localhost chat[8738]:  -- got it
Apr 21 04:23:57 localhost chat[8738]: send (\d)
Apr 21 04:23:58 localhost pppd[8737]: Serial connection established.
Apr 21 04:23:58 localhost pppd[8737]: Using interface ppp0
Apr 21 04:23:58 localhost pppd[8737]: Connect: ppp0 <--> /dev/ttyS0
Apr 21 04:23:59 localhost pppd[8737]: CHAP authentication succeeded
Apr 21 04:24:00 localhost pppd[8737]: local  IP address xxx.xxx.xxx.xxx
Apr 21 04:24:00 localhost pppd[8737]: remote IP address xxx.xxx.xxx.xxx
Apr 21 04:24:00 localhost pppd[8737]: primary   DNS address
xxx.xxx.xxx.xxx
Apr 21 04:24:00 localhost pppd[8737]: secondary DNS address
xxx.xxx.xxx.xxx

Here's /var/log/message from the (broken) network-admin session:
Apr 21 04:21:14 localhost pppd[8546]: pppd 2.4.2 started by root, uid 0
Apr 21 04:21:14 localhost pppd[8546]: Removed stale lock on ttyS0 (pid
8326)
Apr 21 04:21:15 localhost chat[8549]: timeout set to 60 seconds
Apr 21 04:21:15 localhost chat[8549]: abort on (ERROR)
Apr 21 04:21:15 localhost chat[8549]: abort on (BUSY)
Apr 21 04:21:15 localhost chat[8549]: abort on (VOICE)
Apr 21 04:21:15 localhost chat[8549]: abort on (NO CARRIER)
Apr 21 04:21:15 localhost chat[8549]: abort on (NO DIALTONE)
Apr 21 04:21:15 localhost chat[8549]: abort on (NO DIAL TONE)
Apr 21 04:21:15 localhost chat[8549]: abort on (NO ANSWER)
Apr 21 04:21:15 localhost chat[8549]: send (ATZ^M)
Apr 21 04:21:15 localhost chat[8549]: send (AT&FH0L1^M)
Apr 21 04:21:15 localhost chat[8549]: expect (OK)
Apr 21 04:21:15 localhost chat[8549]: ATZ^M^M
Apr 21 04:21:15 localhost chat[8549]: OK
Apr 21 04:21:15 localhost chat[8549]:  -- got it
Apr 21 04:21:15 localhost chat[8549]: send (ATDTxxxxxxxxxxx^M)
Apr 21 04:21:15 localhost chat[8549]: timeout set to 75 seconds
Apr 21 04:21:15 localhost chat[8549]: expect (CONNECT)
Apr 21 04:21:15 localhost chat[8549]: ^M
Apr 21 04:21:36 localhost chat[8549]: ATDTxxxxxxxxxxx^M^M
Apr 21 04:21:36 localhost chat[8549]: CONNECT
Apr 21 04:21:36 localhost chat[8549]:  -- got it
Apr 21 04:21:36 localhost pppd[8546]: Serial connection established.
Apr 21 04:21:36 localhost pppd[8546]: Using interface ppp0
Apr 21 04:21:36 localhost pppd[8546]: Connect: ppp0 <--> /dev/ttyS0
Apr 21 04:21:38 localhost pppd[8546]: CHAP authentication succeeded
Apr 21 04:21:38 localhost pppd[8546]: local  IP address xxx.xxx.xxx.xxx
Apr 21 04:21:38 localhost pppd[8546]: remote IP address xxx.xxx.xxx.xxx
Apr 21 04:21:38 localhost pppd[8546]: primary   DNS address
xxx.xxx.xxx.xxx
Apr 21 04:21:38 localhost pppd[8546]: secondary DNS address
xxx.xxx.xxx.xxx

(They look very similar to me). Does anyone here understand how these
two mechanisms work enough to help me debug this problem?

Thank you, Jaime