A number of users attempting to update to iOS 4.0.2 have reported problems updating, including “Error 9″ and another issue in which the update stalls partway through.
Fixes
Restore instead of update. Backup your iPhone, then perform a restore process instead of using the check for update function. This may allow the iPhone to successfully receive the iOS 4.0.2 update, after which sync processes should occur at normal speed.
Switch USB ports. Try switching your iPhone to a different USB port. In particular, if you are using a hub or other intermediary device, try connecting the device directly to your computer.
Disable network connection. In some cases, simply disabling your network connection (turning off AirPort or unplugging your Ethernet cable) right after you click the update button will resolve the slow or stuck backup phase. It appears that iTunes performs some data network data transfer during the backup process which can, for unknown reasons, take an extremely long time or become stalled.
Delete backup folder. If you are using a Mac, navigate to (your username)/Library/Application Support/MobileSync/Backup/ and delete the most recent backup folder.
If you are using Windows, delete the most recent backup folder from C:\Documents and Settings\Application Data\Apple Computer\MobileSync\Backup\.
Disable antivirus software. If you are using Windows, try temporarily disabling antivirus software before applying the update.
August 18, 2010 at 2:11 AM
I tried all the ways and i’m still with the progress bar stuck at 50%
Apple is insane releasing updated without testing them! Even discussions on the apple forums are not answered by apple!
Is there any other way to get back to my previous state without loosing data?
August 22, 2010 at 6:14 AM
After trying the advice here, I still had no luck. A post on another site suggested Recboot to get the iPhone out of recovery mode to let you do a standard restore, instead of a recovery restore which is somehow different.
Recboot did the trick. iPhone came right out of recovery mode and a standard restore, from the backup that iTunes took before beginning the upgrade to 4.02, brought the phone back to life, with no apparent issues.
August 22, 2010 at 7:57 PM
Agreed, everybody try recboot.
I tried literally everything for about 5 hours to resurrect this damn phone. And then one click in recboot did it… what a waste of lifetime, thanks apple!
August 25, 2010 at 2:56 PM
My phone is in constant Recovery Loop, tried to stopped that by using Recboot and clicking ‘Exit recovery mode’ nothing happens :/
any tips guys? Thanks!
September 1, 2010 at 5:03 AM
hello ,
had the edge, 3g,3gsn,the 4 is a calamity
I had same problem during 4.01 installation. After that bugs on few appls and phone app !!! I thought the 4.02 would be better. during restore mode it stops just in the middle error 9. I did it with 2 diferents pc one xp one 7. I dont have phone anymore. Iwill buy the first window phone 7 next month ! have a good day whitout apple
denis
November 26, 2010 at 12:26 PM
After installing the software update it has lost all of my contacts!!!
I have tried to re-install using the last back up but it has still not worked. Can anyone help?
November 28, 2010 at 10:19 AM
recboot worked for me, and i also tried restoring mi ipad like 6 hours yesterday.
December 19, 2010 at 5:04 PM
I am getting constant error 9 I have tried everything, DFU mode, recovery mode restores , have tried on different comps/cables nothing works always comes up as error 9. Before this my phone is stuck in a constant black apple screen loop please help I really don’t know what else to do
June 20, 2011 at 7:38 PM
It is a big problem. I updated my iphone to the latest recommended software all went fine untill it stopped and said it coulnt continue and entered recovery mode. Nothing worked to get it out of recovery or to reload it. Not recboot, umbrella nothing….Its off to the apple store for me. I recommend NOT to update your iphone 4 software when prompted on apple itunes because your perfectly well working phone may become a dud in minutes leaving you with hours of troubleshooting to do…..I will wait until apple resoves this issue before updating in the future….