This post only applies if the following conditions are true
- The iPhone boots up and stays in Apple Logo screen forever
- When connected to iTunes, the iPhone is detected properly and shown as connected

I thought my iPhone was gone :)

I had Siri installed in my iPhone 3GS and downgraded my baseband using 'redsn0w_win_0.9.14b1'. It worked fine and booted up. I removed Mobile Substrate and other Cydia apps and the phone was updating SpringBoard. After sometime it was still updating and I reset the phone. When it rebooted, it was stuck at boot logo screen. After trying to jailbreak again couple of times without any result, I figured "Restore" was the only option left. I tried restoring with custom firmware but got Error 3194. I was totally damned. Then I stumbled across this post.

I think the issue was with either Siri or some other Cydia app (I had OpenBackup restoring my Cydia apps and waiting for a reboot). cartoon156 has mentioned a similar issue and reason was siriport entry in SpringBoard not being handled after removing 'Acid'. So, generally the issue seems to be related to Siri.

The fix is simple, just replace SpringBoard configuration with a working config from another iDevice.

Reference: I found it at [How to] Unbrick Your iDevice Stuck at Apple Logo Without Restoring (iOS 5.1.1), all thanks goes to the author :)

I am rephrasing the base steps in case the site is down. Also, I have uploaded the zip to a new location as the link in the site is almost down.

1. First off, to ensure you are in a similar situation to what I was in (as that's what this guide is for), carry out the following sub-steps:

i) Download and install i-FunBox on your PC. Download link
ii) Open iTunes and then connect your bricked iDevice to your computer via a USB cable. Wait for iTunes to detect the iDevice.
iii) Open i-FunBox.
iv) Did i-FunBox detect and display a branch menu of your iDevice (stating it is running iOS 5.1.1) below it's "Connected Devices" branch?
If it did, then you're in the same situation as I was and can safely proceed to step 2.
Otherwise, STOP here and find an alternative solution. As far as I know, this shouldn't cause any issues except deleting all the Cydia apps.

2. Keeping i-FunBox open and your bricked iDevice connected, download the following package and extract it to a on your computer (like your Desktop):

Download: iOS_5.1.1_iDevice_Unbricker_Package.zip

3. Using i-FunBox, copy the "com.apple.SpringBoard.plist" file in the "SpringBoard Launch Daemon (iOS 5.1.1)" folder over to the following directory:

//System/Library/LaunchDaemons

4. Using i-FunBox, copy the contents of the "XXAP.plist Files (iOS 5.1.1)" folder over to the following directory:

//System/Library/CoreServices/SpringBoard.app

5. Reboot your iDevice by simultaneously holding down the "Power/Sleep" button and the "Home" button until the iDevice's screen shuts off, turns back on, and the Apple Logo reappears.

NOTE:
* If you were previously updating a Siri port before you bumped into this issue, you might have to go into Cydia and reinstall it in order for it to be fully functional again.
* On the contrary, if you were previously uninstalling a Siri port, you might have to go into Cydia and confirm it is fully uninstalled.

There you go, you should be good to go :)

On a side note, I finally got my iPhone baseband downgraded to 05.13.04 after using this guide: How To: Downgrade iPhone 3G/3GS Baseband From 06.15.00 To 05.13.04 With RedSn0w 0.9.14b1 [Windows]. Now my GPS is working again. Kudos to redsn0w team :)

If this worked for you OR didn't work for you, please let other know in comments...

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