Mac OSX 10.5.6 may not recognize your iPhone in DFU Mode, an essential facet of jailbreaking and unlocking your iPhone.
DFU (Device Firmware Upgrade) mode allows you to upgrade or downgrade your iPhone OS, bypassing your current OS.
If you have attempted to use QuickPwn or PwnageTool to modify your iPhone on Mac OSX 10.5.6, you may notice that it hangs when it attempts to access your iPhone in DFU mode. To re-enable recognition follow the steps below.

Quick Fix:
Download and install Mac OS X 10.5.5 9F33 IOUSBFamily.kext 315.4 from Apple’s Developer Connection*.
Reboot your Mac.
To Reapply 10.5.6 Update:
Download and install Mac OS X 10.5.6 9G55 IOUSBFamily 327.4 from Apple’s Developer Connection.
Reboot your Mac.
Tips:
-Make sure to not have any additional USB peripherals attached
(that includes a USB hub)
-You must Reapply 10.5.6 Update, otherwise your Macbook will crash upon plugging in more than 2 USBs at a time.
*You need to sign up for a free account if you don’t already have one.
