Демон gammu-smsd не отправляет SMS-сообщения

Я заметил, что мой демон gammu-smsd, работающий в Ubuntu, внезапно не отправляет сообщения (таблица sentitems моей базы данных postgresql не обновляется). Сначала я заметил, что damemon не работает, поэтому я перезапустил его:

$ sudo /etc/init.d/gammu-smsd start
 * Starting Gammu SMS Daemon gammu-smsd    [ OK ]

Затем я проверил системный журнал (это журнал, для которого я настроил gammu-smsd для отчета):

Jun 27 15:33:04 porkypig gammu-smsd[19267]: Configuring Gammu SMSD...
Jun 27 15:33:04 porkypig gammu-smsd[19267]: SHM token: 0xffffffffce020154 (-838729388)
Jun 27 15:33:04 porkypig gammu-smsd[19267]: Warning: No PIN code in /etc/gammu-smsdrc file
Jun 27 15:33:04 porkypig gammu-smsd[19267]: commtimeout=30, sendtimeout=30, receivefrequency=0, resetfrequency=0
Jun 27 15:33:04 porkypig gammu-smsd[19267]: checks: security=1, battery=0, signal=1
Jun 27 15:33:04 porkypig gammu-smsd[19267]: deliveryreport = no
Jun 27 15:33:04 porkypig gammu-smsd[19267]: phoneid =
Jun 27 15:33:04 porkypig gammu-smsd[19268]: Using PGSQL service
Jun 27 15:33:04 porkypig gammu-smsd[19268]: Connected to database: smsd on localhost. Server version: 80414 Protocol: 3
Jun 27 15:33:05 porkypig gammu-smsd[19268]: Database structures version: 11, SMSD current version: 11
Jun 27 15:33:05 porkypig gammu-smsd[19268]: Table check succeeded
Jun 27 15:33:05 porkypig gammu-smsd[19268]: Starting phone communication...
Jun 27 15:33:22 porkypig gammu-smsd[19268]: Error at init connection No response in specified timeout. Probably phone not connected. (14)
Jun 27 15:33:22 porkypig gammu-smsd[19268]: Terminating communication No response in specified timeout. Probably phone not connected., (14, 250 times)
Jun 27 15:33:22 porkypig gammu-smsd[19268]: Starting phone communication...
Jun 27 15:33:32 porkypig gammu-smsd[19268]: Error at init connection No response in specified timeout. Probably phone not connected. (14)
Jun 27 15:33:32 porkypig gammu-smsd[19268]: Terminating communication No response in specified timeout. Probably phone not connected., (14, 250 times)
Jun 27 15:33:32 porkypig gammu-smsd[19268]: Starting phone communication...
Jun 27 15:33:42 porkypig gammu-smsd[19268]: Error at init connection No response in specified timeout. Probably phone not connected. (14)
Jun 27 15:33:42 porkypig gammu-smsd[19268]: Terminating communication No response in specified timeout. Probably phone not connected., (14, 250 times)
Jun 27 15:33:42 porkypig gammu-smsd[19268]: Starting phone communication...
Jun 27 15:33:52 porkypig gammu-smsd[19268]: Error at init connection No response in specified timeout. Probably phone not connected. (14)
Jun 27 15:33:52 porkypig gammu-smsd[19268]: Terminating communication No response in specified timeout. Probably phone not connected., (14, 250 times)
Jun 27 15:33:52 porkypig gammu-smsd[19268]: Going to 30 seconds sleep because of too much connection errors
Jun 27 15:34:22 porkypig gammu-smsd[19268]: Starting phone communication...
Jun 27 15:34:32 porkypig gammu-smsd[19268]: Error at init connection No response in specified timeout. Probably phone not connected. (14)
Jun 27 15:34:32 porkypig gammu-smsd[19268]: Terminating communication No response in specified timeout. Probably phone not connected., (14, 250 times)
Jun 27 15:34:32 porkypig gammu-smsd[19268]: Going to 30 seconds sleep because of too much connection errors
Jun 27 15:35:02 porkypig gammu-smsd[19268]: Starting phone communication...
Jun 27 15:35:12 porkypig gammu-smsd[19268]: Error at init connection No response in specified timeout. Probably phone not connected. (14)
Jun 27 15:35:12 porkypig gammu-smsd[19268]: Terminating communication No response in specified timeout. Probably phone not connected., (14, 250 times)
Jun 27 15:35:12 porkypig gammu-smsd[19268]: Going to 30 seconds sleep because of too much connection errors
Jun 27 15:35:42 porkypig gammu-smsd[19268]: Starting phone communication...
Jun 27 15:35:52 porkypig gammu-smsd[19268]: Error at init connection No response in specified timeout. Probably phone not connected. (14)
Jun 27 15:35:52 porkypig gammu-smsd[19268]: Terminating communication No response in specified timeout. Probably phone not connected., (14, 250 times)
Jun 27 15:35:52 porkypig gammu-smsd[19268]: Going to 30 seconds sleep because of too much connection errors
Jun 27 15:36:22 porkypig gammu-smsd[19268]: Starting phone communication...
Jun 27 15:36:32 porkypig gammu-smsd[19268]: Error at init connection No response in specified timeout. Probably phone not connected. (14)
Jun 27 15:36:32 porkypig gammu-smsd[19268]: Terminating communication No response in specified timeout. Probably phone not connected., (14, 250 times)
Jun 27 15:36:32 porkypig gammu-smsd[19268]: Going to 30 seconds sleep because of too much connection errors     

Означает ли это, что модем, подключенный к последовательному порту компьютера, не отвечает? (Я получаю доступ к машине через ssh и не хочу, чтобы физически приходил на компьютер, если это не требуется.)

Обратите внимание, что я могу бежать sudo minicom и получите следующее:

Welcome to minicom 2.4

OPTIONS: I18n 
Compiled on Jan 25 2010, 07:02:36.
Port /dev/ttyS0

Press CTRL-A Z for help on special keys  

Тем не менее, minicom не позволяет мне вводить команды at в окне. Это просто показывает мигающий курсор. Хотя я могу использовать сочетания клавиш CTRL-A Z и другие сочетания клавиш CTRL-A для доступа к меню, я не могу вводить какие-либо команды at в окне.

Журнал Minicom выглядит так:

$ cat minicom.log
20130610 17:57:50 Hangup (0:10:29)
20130611 10:47:56 Gone offline (0:00:02)
20130611 10:53:59 Hangup (0:00:00)
20130611 12:51:50 Hangup (0:00:00)
20130612 00:43:39 Hangup (0:00:00)
20130616 21:45:54 Hangup (0:00:07)
20130624 14:22:48 Hangup (0:01:43)
20130624 14:26:02 Hangup (0:02:58)
20130624 16:58:52 Hangup (2:19:25)
20130625 15:04:39 Hangup (0:03:54)
20130626 10:43:19 Hangup (0:08:13)
20130627 15:46:02 Hangup (0:00:35)

Есть идеи, почему SMS-сообщения не отправляются?