Some users recently reported that the newest version of Mac OS X update ruined the DFU mode and their iPhone can not be detected in that mode. First reported at iSpazio but then later confirmed by others. 

     This issue is the same as the one with new macbooks. Some have even confirmed that the error message is even the same one. This is again a major drop back for those who want to jailbreak their phones in the future and keep the mac up-to-date. Some reports claim that connecting the iPhone to a USB hub, instead of directly connecting it the MAC will help solve the problem.

     When the DevTeam were informed about this, they soon posted an update on their site. They don’t think it is a countermeasure by Apple but just a bug. Though they have suggested some ways to bypass the problem, they warn you to try them at your own risk in their usual manner!

     “1. Replace the following plugin kexts from within IOUSBFamily.kext with the ones from 10.5.5 and then rebuild kextcache (if you don’t understand this, then you shouldn’t attempt it!)

     /System/Library/Extensions/IOUSBFamily.kext/Contents/PlugIns/
AppleUSBHub.kext

     /System/Library/Extensions/IOUSBFamily.kext/Contents/PlugIns/
IOUSBCompositeDriver.kext

     2. Use a USB hub in-between the DFU device and the Mac and insert/reinsert the iPhone’s USB cable.

     3. Use the PwnageTool created .ipsw on Windows! Oh the irony!”

     For now these are the only ways out for you, but hopefully Apple will solve the problem soon if it’s actually a bug. Also, for all the Windows users, you don’t need to worry as this problem is Mac exclusive.