As you guys already know, there's a new version for iPod firmware 1.1.5. To my honest opinion, DO NOT UPGRADE YET! There's no known methods for downgrading, conventional "DFU-Restore" doesn't seems to work like it used to for firmware 1.1.4.
Also, try not to update iTunes unless you're absolutely sure of what you're doing.
END OF UPDATE
Anyway, purpose of this post is to outline most of the errors you might encounter, and it's solution.
Let's get started!
Unknown error (1)
This error is irritating. If the iPod Touch can talk, it'll probably say: "Hahahaha! Serves you right for upgrading me to 1.1.3, then trying to downgrade. Now I'm gonna tell you that, FUCK NO I'm going to let you downgrade."
So the solution? Make your iPod Touch in DFU Mode prior to downgrading. It's not easy to execute, some people reported to having it trying up to 16 (that's sixteen) times before it's successful. Remember, patience pays for your ignorance. :)
Error 1403 | Error (1403)
In some cases, you might hit this error. Even though you selected the right file, with the right extension, this error shows up unexpectedly.
Solution? Download the firmware again. But before you do that, make sure you clear your internet explorer cache (or firefox cache) then download the firmware again. Make sure you select the right one for the right device.
To find out if you are having the uncorrupted file, do this:
Step 1: Copy that _Restore.ipsw file into another file (you can simple copy and paste, it's probably comes out as a "copy of..." file)
Step 2: Change the extension of that into a *.zip file. Simply rename the *.ipsw into *.zip
Step 3: Try unzipping it (as how you usually unzip files). If it unzips successfully, it's not a corrupted file.
For a list of firmwares, visit here.
Error 1604 | Error (1604)
This error is a special case. It have something to do with iTunes. If you're using iTunes lower that 7.5, you will need to update it. Preferably use 7.5.
Here are some related links for you to digest on.
Removing iTunes, QuickTime, and other software components for Windows XP
Error 1604 When restoring iPhone in iTunes
iPod touch not recognized in iTunes for Windows
Error 1601, Error 1602 | Error (1601), Error (1602)
This one is about the same as the above.
Recommended solution: Update to iTunes 7.5 or greater.
Error 1601 or 1602 when restoring iPhone or iPod touch in iTunes
Unknown error (0xE8000022)
You will most likely hit this error as a sync-ing problem. "Itunes could not connect to the iPod “iPod” because an unknown error occurred (0xE8000022)"
The real solution is yet to be discovered, however, I have figured some temporary workaround for it. If you know of a better solution, please do let me know.
Kills "iTunesHelper.exe" background service
It seems that something in the background is preventing your device from getting connected. Try killing all background services that have the word "iPod", "iTunes" or "Apple" in them. Then re-launching iTunes.
I don't know what you're trying to do, but if you can't connect to the device, probably it have something to do with iTunes.
Restore your iPod
Restoring definitely helps in any situation.
This is a SUPER tricky one. Because there's no related issues to this error.
Solution: Whenever you hit an unknown error (without any numbers), it's probably because of iTunes. I suggest restarting the comp or reinstalling iTunes (preferaby 7.5). Sometimes, a simple retry might help.
Help! I got any other errors other than those listed here!
Then use the comment feature. Although it's to comment on the post, but it have become a "I got a question!" feature. Use it well. And I'll try my best to reply when I'm available.