Yes I did many times. If you don't restart, phone might crash when you try to open Cellular data network.
Even restored many times in MAC and PC.

With MAC, iTunes still check for carriers update.
With PC, it doesn't do the checking anymore. Apple changed something with newest PC iTunes version.

Umm, I think I know a way to fix this. I'll try when I get home.

i get a blank cellular data network... tried everything.

MMS and Data is working for me though... haven't tested terthering

if you patched with an ipcc custom file, i may have a solution for you.

restore to 2.2.1. when the restore is completed, I believe iTunes will ask you if you want to update carrier settings. that may fix the problem.

I don't think the blank page problem is the custom file. It's the beta 3 bug or apple meant to do that.
But I edited it in beta 2 and upgrade to beta 3, my data works now. That's all I need.

You are not the only one. My cellular data network menu is blank as well.

I also have problems with editing the APN setting for my carrier (Tele2 in Sweden).
I understand I should create my own .ipcc in order to fix my apn and maybe get my MMS working.

At the moment I have an officially unlocked iphone 3g on beta3 (using tele2 carrier), jailbroken with ssh and have icy installed.

I wish to enable my apn so I can set it to internet.tele2.se, how can you create your own .ipcc for 3.0?

@barhom

Try this maybe..

probably works out good. My problem is that Im on windows and I cant seem to get pledit.exe working so I can edit the .plists :/

The right person maybe knows what he/she can produce out of all this information: (creation of an unsupported carrier)

MCC/MNC:
24005
24007

Carriername: Tele2
AllowPrefixMatching:
S COMVIQ -> Tele2
SWEDEN 3G -> Tele2

PNG's should be for Tele2.

APN: internet.tele2.se
Username: leave empty
password: leave empty

MMS:

mms_proxy: 130.244.202.30
port: 8080
mmsc: http://mmsc.tele2.se

AllowAPNEditing, mmsediting etc etc all should be on.

These should be false: (they are annoying)
<key>ShowCallForwarded</key>
<false/>
<key>ShowCallForwarding</key>
<false/>
<key>ShowDialAssist</key>
<false/>

If somebody knows how to make a PROPER ipcc out of this I would be very glad, and by seeing how it will be written I will make a php generator for this. Ive been trying it for 8hrs now and Im tired of all this ipcc creating

Guys just download the iPhone configuration utility from apple, email yourself the .mobileconfig file with APN settings and there u go