Help: Cannot upgrade to iOS4

if i were u i wouldnt do it. i put ios4 on my moms 3g and it runs like crap now... just a warning haha

 

Go to the appropriate FORUM = iPhone HACKS

 

+1
Don't do it! I upgraded my 3G when 4.0 came out and it was awful...lagged, dragged, bugs, etc. I just downgraded back to 3.1.3 and feel like I actually upgraded, it's so much more responsive. I almost forgot how the phone should work. Much better now/again. So, I can now (soon) move up to iPhone 4 and hand down my 3G to my girlfriend with a clean conscious.

 

You could do an itunes uninstall/re-install, etc, etc,

But as most have said ios4 on the 3G will depress you!

 

+ another one. Am just going through a downgrade on my 3G at this moment because of how slow it turned out to be. Fingers crossed that it goes well.
As to unlocking the handset.. I am with Optus in Australia. I called them six weeks ago to prep for using foreign sims in the UK, France and Italy when travelling in September, and they sms'd me a code a code a couple of days later; backup/restore in iTunes and I had an unlocked 3G on 3.1.3. Hopefully AT&T will do the same for you.
Now waiting for the 4 to come to Oz...maybe August??

 

Did you change your hosts file? If you did you need to change it back to the original and try again...

 

I would not put iOS4 on a 3G phone.