Not long ago, I received a 1015 error message stating I could not upgrade, downgrade nor restore my iPhone 3GS (I am sure this fix will work for other models). This was because, I tried to upgrade my iPhone while it was Jailbroken. This is a new bug that has appeared. I know this because I done 8 hours Googling, forum searching everything about and of the problem, nothing helpful was found. But except a few useful posts about the apps: iReb, Redsn0w, sn0wbreeze & TinyUmbrella. If this is your problem, you need to follow these steps.

Note: Date may vary and versions may be newer. This is strictly for the current iOS 4 firmwares. In-case this may not work, try downloading all the firmwares in the iOS 4 and then trying the steps below.

  1. You firstly need to download the following (exact versions):
    iREB 4.0.x-4.1-RC2
    redsn0w 0.9.6b4
    If your asking for the download links, just bloody Google them.
  2. Firstly, download your last known firmware (4.1 for the newer 3GS's) (Google "ipsw" for this)
  3. Extract all of them to your Desktop or into 1 folder of your choice.
  4. Run sn0wbreeze and use the firmware (4.1) you just downloaded. Use simple mode and it will then drag a new type of ipsw to your folder or desktop. Once thats done, run through iReb if sn0wbreeze hasn't done that yet for you.
  5. Close iTunes. Open up TinyUmbrella and hit, Run TSS Server.
  6. Open up your host file in your C:\Windows\System32\Drivers\etc\ and double check, at the end, there's something called If there is your good to go.
  7. Open iTunes and hold down control and click the Restore button.
  8. Open the one custom-ipsw that sn0wbreeze created for you in step 4 and let it do the magic.
  9. Once it's done, it should give you a black screen on your iPhone.
  10. Final step is to run redsn0w and open the FIRMWARE YOU DOWNLOADED, not the custom one and boot in tethered.