hello all,
yesterday i updated to 3.0 on my 2g iphone wid redsnow, evrything works gr88, but now i donot see any feild in settings > network for adding my apn settings to activate edge.. kindly help..

i guess is in file private/var/preferences/SystemConfiguration/preferences.plist but i didn't check that - APN username and password are there.

i lost my edge settings when i was trying to get mms and tethering working. i found the carrier ipcc files (tmobile/att) and loaded that on the phone to get the edge options back on the phone.
iPhone 3.0 [MMS] [Tethering] [VVM] *AT&T* and *T-Mobile* | TheLeanProject.Com

The way I fixed this on my jail broken 2g iphone (back in the 2.2.1 days) was to go into settings->general->reset->reset network settings (then select reset)

Once that was done (I think it restarted or required one), the option to change my apn settings was there under settings->general->network->cellular data network.

I had tried the cydia apn hack and various other things but in the end, after a ton of nail biting and hair pulling, this is what worked. I hope it does for you too.

Or you can install pack "APN editing" from Cydia.

I tried the cydia hack and it didn't work. In the end, on;y resetting netwoek settings, and restarting the iphone, enabled the ability to manually change apn settings.

I tried both Cydia and resetting network setting - none of this solution worked for me.

I too upgrade my jailbroken and unlock Iphone 2G to OS 3.0 today and everything is working fine except EDGE.

Can someone please let me know to how to get rid of this problem or how to downgrade iphone from 3.0 to 2.2.1

thanksss the cydia hack worked for me

same here.
non of the solutions listed above worked for me.

i tried "apn editing" from cydia it didn't work.

also reseting all network settings didn't work.

does anyone knows the solution?

My best guess that it didn't work cause it seems that when your phone provider has the settings in the SIM already the iphone won't show the Settings->General->Network->Cellular Data menu option, just a guess cause for me my provider here in Argentina same thing happens, but MMS is working perfectly.