As mentioned, this problem persists after upgrading to intrepid. I now have a Nokia E66, which is a fairly new model, and hence there is very little information available as to how this problem affects others. 

When I plug in the phone, the phone asks me whether to plug in as mass storage device, pc suite connection or modem, but linux mounts the card correctly whether i make a selection or not. 

At this point the output of 
$ lsusb -m

Start monitoring devicelist:
-------------------------------------------------
09:22:35.331: usb_device_421_af_352942020124803 added
09:22:35.379: usb_device_421_af_352942020124803 property info.linux.driver = 'usb' (new)
09:22:35.590: usb_device_421_af_352942020124803_if0 added
09:22:35.767: usb_device_421_af_352942020124803_if0_scsi_host added
09:22:40.452: usb_device_421_af_352942020124803_if0_scsi_host_0 added
09:22:40.470: usb_device_421_af_352942020124803_if0_scsi_host_0_scsi_device_lun0 added
09:22:40.839: usb_device_421_af_352942020124803_if0_scsi_host_0_scsi_device_lun0_scsi_generic added
09:22:42.557: storage_serial_Nokia_E66_352942020124803_0_0 added
09:22:42.670: storage_serial_Nokia_E66_352942020124803_0_0 property info.interfaces = {'org.freedesktop.Hal.Device.Storage.Removable'} (new)
09:22:42.900: volume_uuid_0331_5F86 added
09:22:43.242: volume_uuid_0331_5F86 property volume.mount_point = '/media/nokia4gb'
09:22:43.250: volume_uuid_0331_5F86 property volume.is_mounted = true


and of
$ dmesg
[35317.580059] usb 2-2: new full speed USB device using uhci_hcd and address 3
[35317.801059] usb 2-2: configuration #1 chosen from 1 choice
[35317.840867] scsi5 : SCSI emulation for USB Mass Storage devices
[35317.842375] usb-storage: device found at 3
[35317.842388] usb-storage: waiting for device to settle before scanning
[35322.841269] usb-storage: device scan complete
[35322.844258] scsi 5:0:0:0: Direct-Access     Nokia    E66              1.0  PQ: 0 ANSI: 0
[35322.871855] sd 5:0:0:0: [sdc] 7856128 512-byte hardware sectors (4022 MB)
[35322.875189] sd 5:0:0:0: [sdc] Write Protect is off
[35322.875205] sd 5:0:0:0: [sdc] Mode Sense: 03 00 00 00
[35322.875214] sd 5:0:0:0: [sdc] Assuming drive cache: write through
[35322.918082] sd 5:0:0:0: [sdc] 7856128 512-byte hardware sectors (4022 MB)
[35322.927327] sd 5:0:0:0: [sdc] Write Protect is off
[35322.927346] sd 5:0:0:0: [sdc] Mode Sense: 03 00 00 00
[35322.927354] sd 5:0:0:0: [sdc] Assuming drive cache: write through
[35322.928556]  sdc:
[35323.110337] sd 5:0:0:0: [sdc] Attached SCSI removable disk
[35323.113821] sd 5:0:0:0: Attached scsi generic sg2 type 0

Now i go to nautilus to unmount the device, and this has no effect on dmesg or on the device, but adds this to the lsusb -m output

09:27:24.336: volume_uuid_0331_5F86 property volume.mount_point = ''
09:27:24.368: volume_uuid_0331_5F86 property volume.is_mounted = false

So i try 
$ sudo eject /dev/sdc  (which used to work with my nokia 6110 phone)

and this command takes 30 seconds to complete and has no effect on lsusb -m, but adds these lines to dmesg output:

[35702.960138] usb 2-2: reset full speed USB device using uhci_hcd and address 3
[35713.220064] usb 2-2: reset full speed USB device using uhci_hcd and address 3

But still no effect on the phone.

With older kernels it was possible to echo a "1" directly into sysfs power/state file for the device, but that file doesn't seem to exist with newer kernels, so i'm pretty much stuck for now. 
If i disconnect the phone at this point everything sems to be fine, until i open an application that reads from the memory card (usually the music player). At this point the phone sometimes tells me it needs to repair a corrupted memory card, and spends a good 30 seconds doing that. On other occasions it seems to work fine, so i'm not sure what the net effect of this issue is except that it's a bit disconcerting that unmounting in nautilus doesn't work, and that even after using the eject command with sudo i get no feedback.

Let me know what other info you might need.