no sound from line-in

I used the last version of Ubuntu 7.10 (update from 7.04)
When I attached a microphone to my Ubuntu, I cannot here anything and the problem is because of line in!
When I select ALSA for "Default Input" in "Multimedia Systems Selector", it return an error: "Failed to construct test pipeline for ALSA"
And when I run "gnome-volume-control --gst-debug-level=5", I get these errors when I was changing volume of line in:

0:12:05.778478000 776 0x8242710 DEBUG alsa gstalsamixer.c:411:task_monitor_alsa: Handling events
0:12:05.778525000 776 0x8242710 LOG alsa gstalsamixer.c:212:gst_alsa_mixer_elem_handle_callback: ALSA elem cb
0:12:05.778542000 776 0x8242710 DEBUG alsa gstalsamixer.c:801:gst_alsa_mixer_update_track: Updating track <GstAlsaMixerTrack@0x8197ae0>
0:12:05.778592000 776 0x8242710 LOG GST_MESSAGE gstmessage.c:204:gst_message_init: new message 0x829b080
0:12:05.778609000 776 0x8242710 LOG GST_MESSAGE gstmessage.c:287:gst_message_new_custom: source alsamixerelement0: creating new message 0x829b080 element
0:12:05.778627000 776 0x8242710 LOG GST_REFCOUNTING gstobject.c:325:gst_object_ref:<alsamixerelement0> 0x818d068 ref 8->9
0:12:05.778644000 776 0x8242710 DEBUG default gstelement.c:1555:gst_element_post_message:<alsamixerelement0> not posting message 0x829b080: no bus
0:12:05.778661000 776 0x8242710 LOG GST_REFCOUNTING gstminiobject.c:312:gst_mini_object_unref: 0x829b080 unref 1->0
0:12:05.778676000 776 0x8242710 LOG GST_MESSAGE gstmessage.c:213:gst_message_finalize: finalize message 0x829b080
0:12:05.778692000 776 0x8242710 LOG GST_REFCOUNTING gstobject.c:352:gst_object_unref:<alsamixerelement0> 0x818d068 unref 9->8
0:12:05.778708000 776 0x8242710 WARN default mixer.c:464:gst_mixer_volume_changed: This element has no bus, therefore no message sent!
0:12:05.778728000 776 0x8242710 LOG alsa gstalsamixer.c:404:task_monitor_alsa: task loop