iPhone Dev Team has pushed a minor update to its redsn0w jailbreak tool upgrading it to version redsn0w 0.9.10b6b for Mac OS X. According to change log redsn0w 0.9.10b6b download fixes a compatibility issue for those running Mac OS X 10.5.x or earlier when trying to jailbreak iOS 5.1 on iPhone 4, iPhone 3GS, iPod touch 4G/3G including first generation iPad. This update do not support iPhone 4S or iPad.

Many user who downloaded redsn0w 0.9.10.b6, complained that the tool correctly recognize his iOS device. But when they try to go into DFU mode either before or during the jailbreak process, it refers them to search on Google on how to enter DFU mode message. It just does not pick up their device correctly after going through the required steps.
Users who are using OS X 10.5.x or earlier and are affected by redsn0w 0.9.10b6, must download the updated and correct version of Redsn0w 0.9.10b6b before trying to jailbreak iPhone, iPod touch or iPad. The guide for jailbreaking iOS 5.1 IPSW will remain same for all supported iOS devices for both Windows and Mac OS X platform.
Redsn0w 0.9.10b6b Download links:

If you would like to downloadRedSn0w0.9.10b6b for Windows or Mac OS X you can go to the our dedicated jailbreak tool section or use one of the direct download links shown below.
Download RedSn0w 0.9.10b5c (Windows)
Download RedSn0w 0.9.10b5c (Mac OS X)