Users are advised not to do so, because jailbreak GUI's like QuickPwn and Pwnage Tool doesn't not work with iTunes 8.2. If your iPhone is already jailbroken, it should work flawlessly though.

HELP NEEDED.
Here's the case. (happens to one of my friend)

iPhone Generation : iphone 3G 8GB
Unlocked? (or Part Number): Unlock using software (i think, because this fella bought his iphone from china, come ready unlock with cydia installed, but after upgraded to 3.0 the phone locked! - only can do emergency call, seriously this is officially locked iphone and he didnt know it)
Current Firmware : 3.0 (prev 2.2)
iTunes Version : 8.2
Model Number : sorry i cant provide this as the phone already locked when i get it (i'm only try to recover)
PC/MAC : PC
Jailbreaking software :
Problem Encountered :
1. Upgrade from 2.2 to OS 3.
2. At last stage, error at itunes said that "Sim is not support by carrier" (something like that)
3. When remove iphone and try to detect it again at iTunes, below error popup:
"iTunes cannot connect to the iphone because it is lock with a passcode. You must enter the passcode on the iphone before it can be used with iTunes"
4. The user previously lock his iphone with sim passcode, but now after upgrade, the phone itself also have been locked! (only for emergency call). So now, stuck at phone passcode lock + iphone lock!

Steps Taken So Far :
- I Plan to try downgrade to 2.2.1 :
1. install iTunes 8.1.1 at new PC
2. Connect iphone to the new itunes, but the above error still popup. Try to change another sim also wont work.
3. Try to get the phone into DFU mode, also not success. (using the right sleep + home combination)

Other Information/Remarks :
Tried connect the iphone to iTunes(either 8.2 or 8.1.1), the above error popup, and the worst case is, the iphone is not listed at the right panel of iTunes.
(means that i dont have the "Upgrade" or "Restore" button)

What should i do to help him!

lol, nvm bout that and congrats with the iphone unlock, so its really works then.? i thought we will need to wait for the ultrasn0w for the 3G, anyway i will trying to read and view the process then,( need to unlock my friends brother iphone 3G, from last march he still using the rebel sim for his iphone).. .
cheers.

em, i think its not called unlock but its called activate bypass the activation process(where it shows only emergency call etc)., im not sure because in redsn0w only jailbreak iphone 3G and we will need to wait dev team release the Ultrasn0w for the for phone to use with sim card.( not sure because i read and that what i was assume)

basically there is 3 thing in iphone thingy.

1) activate-is where you enable the phone and use the app inside it( including the calling function if the phone is official unlock)
2) jailbreak- is where the phone will be "software mod"-a look a like and we can get into its root partition and cydia/icy where istalled and we can install third party app that is not in app store.
3) unlock- is where you make the iphone works with any sim card and can make call, and as for iphone 3G firmware 2.2 or 2.2.1 last time using yellowsn0w with baseband 2.28.00 and now there will be an Ultrasn0w for firmware 3.0 baseband 4.26.08 which is not release yet( and will be release soon) so basically we cant make any call with the iphone 3G "locked" set because the ultrasn0w still not release yet.
anyway try to insert your sim card then see if there is any signal from the iphone, try to make some call using that iphone..if ok then i may be wrong and still not read and understanding it 100%..

waiting for your info then.

p/s: anyway if my statement wrong, please anyone correct me..
- oh ya you can activate it your self because activation only do activation, he can snyc with his laptop later when he meet you.