Setting modem or mobile phone as a modem is quite easy on intrepid. just right-click on network manager and set up account of “mobile broadband”.

but As I’m updating my ubuntu. I found strange thing with network-manager. It usually show “Telkomsel” as my mobile broadband connection (I’m using telkomsel flash 3.5G) but now, there isn’t any. try to googling  a bit and came up with this bug

https://bugs.launchpad.net/ubuntu/+source/hal-info/+bug/261416

actually there is a bug on hal-info which already resolved in package hal-info – 20081013-0ubuntu3 but reaper in hal-info_20081124-0ubuntu1.

Something wrong with hal-info that the configuration does not detect E51 as mobile phone. The problem is, product id of nokia E51 does not registered on hal-info hence It couldn’t detect the phone

try lsusb to get the product and vendor info on your usb. Mine is

ahmy@ahmy-desktop:~$ lsusb
Bus 002 Device 005: ID 0421:0042 Nokia Mobile Phones
Bus 002 Device 004: ID 05ac:1209 Apple, Inc. iPod Video
...

look at the id 0421:0042

see that 0421 is the vendor id (nokia), we would write it like this 0×421
and 0042 is the product id (E51) and we also write it like this 0×042

now in order network-manager to detect the pone edit file
/usr/share/hal/fdi/information/10freedesktop/10-modem.fdi

find this line

<!-- Nokia -->
<match key="@info.parent:usb.vendor_id" int="0x421">
<!-- 6300/3109c/6120 Classic/E71/E70/N95-3/E90/N70/E61/N95-2/N96/N82/N82 (alternate chip)/E66 -->
<match key="@info.parent:usb.product_id" int_outof="0x4f9;0x64;0x2f;0xab;0x418;0x4f0;0x4ce;0x43a;0x44d;0x070;0x3a;0x71;0x72;0xb0">
<match key="@info.parent:usb.interface.class" int="0x02">
<match key="@info.parent:usb.interface.subclass" int="0x02">
<append key="modem.command_sets" type="strlist">GSM-07.07</append>
<append key="modem.command_sets" type="strlist">GSM-07.05</append>
</match>
</match>
</match>
</match>

see that product id match “ 0×421” but there are no 0×042. Just append it on the match tag. So it would appear like this
<match key="@info.parent:usb.product_id" int_outof="0x4f9;0x64;0x2f;0xab;0x418;0x4f0;0x4ce;0x43a;0x44d;0x070;0x3a;0x71;0x72;0xb0;0x042">

And reboot your box. Then … voila