So I looked around the forums for similar issues, but found nothing. I'm on a macbook pro (last gen 10.5.6) and on all the most recent updates and using pwnagetool for an 8gb iphone and trying to get to the 2.2.1 firmware. After I enter DFU mode, itunes pops up with "An ipod has been detected, but it could not be identified properly. Plese disconnect and reconnect the iPod, then try again. An unknown error occurred (2001)." When I quit itunes and relaunch it, it gives me the same message. I've tried everything I can think of, but if anyone has experienced and resolved this issue, or has any suggestions, please help.

Same problem .. please help ..

Mac OS X 10.5.6? If so this is the reason. DFU mode is broken there. Search the forum please

Found a solution on MacRumor forum.

No need for a hub. Dev team found a better way. It works fine i used it.
Fixing DFU mode on 10.5.6

As noted previously OS X 10.5.6 introduced a bug that affected the use of DFU mode. with some Macs. There have been previously published hacks and techniques to fix this, but here is another method that can be used to temporarily restore DFU functionality in order to use QuickPwn or PwnageTool.

1. You will need an account with ADC (Apple Developer Connection) this is free and takes a few minutes to sign up, you should read the terms and conditions carefully and you should only sign up if you are thinking of developing applications in the future - Apple Developer Connection - Mac Dev Center
2. Download the disk image “IOUSBFamily-315.4-log.dmg” for Mac OS X 10.5.5 Build 9F33” (yes, that is a “5” in 10.5.5 - this is a developer debug package of the USB kernel extension).
3. Unplug non-vital USB equipment, such as external DVD writers, USB scanners, USB mass storage devices, at the most leave a Keyboard and Mouse connected.
4. Install IOUSBFamily-315.4.1.pkg from within the disk image
5. Reboot your system!
6. Perform necessary DFU activity with QuickPwn or PwnageTool.
7. Download the disk image “IOUSBFamily-327.4.0-log.dmg” for Mac OS X 10.5.6 Build 9G55”
8. Intall IOUSBFamily-327.4.0.pkg from within the disk image
9. Reboot your system!
10. Reattach your USB peripherals.