Well you probably got excited at the news that Siri had been ported to the older iPhones and decided to install it on your iPhone… Like me:P You then found out it hadn’t worked and decided to uninstall it… Only to find your iPhone stuck in a boot loop (unending apple logo). Well I finally found a way (after many bruises to my head) to fix it.
Disclaimer: I am not responsible for any damage done to your phone by following this tutorial. Execute the steps at your own risk!
First of all you will need to put your iPhone in DFU mode. That is done by holding the power and home button for about 10 seconds then releasing the power button, keeping the home button pressed for about 15 seconds. You should now be on a black screen.
Plug-in your phone to iTunes 10.5 and click on Restore. Follow the steps and after about an hour or so your phone should now be running 5.0.1
For Jailbreakers: Get the newest Redsn0w from the Dev-Team Blog
Click on “Extras” and point it to the iOS 5.0 IPSW. Now click “Back” then “Jailbreak” and follow the steps shown. You should now be running a tethered jailbreak for all devices except for iPhone 3Gs old-bootrom (untethered)
Well thats it:) If you have any questions or problems feel free to post them in the comment section.
Attention: For the time being, Ultrasn0w won’t work on iOS 5.0.1 even if you have the corresponding baseband:(
Rebel Dev 
I have the same problem. I am on 3gs baseband 6.15. I can’t go to ios 5.0.1 without a custom IPSW and definitely not without an ultrasn0w. Will I be be able to restore to custom IPSW of ios 5?
Yes of course:) I will be posting a tutorial soon…
Can you just tell me if that is possible – restoring to iOS 5? Since Apple has stopped signing iOS 5.0, can I still restore to iOS 5.0 with a custom fw? Or will I get some error?
If not, can you tell me how to access iPhone file system in DFU mode?
It is possible:) Just finished testing on my phone:)