The iPhone Dev-Team has released RedSn0w 0.9.6b5 for unlockers stuck at the 05.14 or 05.15 basebands.

The new redsn0w 0.9.6beta5 is out. It gives both Windows and OSX users the ability to flash the iPad 06.15 baseband on iPhone3G or iPhone3GS. It fetches the baseband files directly from Apple for now (the only IPSW you ever point it at is the stock IPSW for the FW on your iPhone right now). There may be a long delay while it’s doing this (their servers are getting pounded right now).

You can download the new version of RedSn0w here:
Windows
Mac

iPhone Dev-Team Releases RedSn0w Update for Unlockers (Win/Mac)
من هنا طريقة عمل الجلبريك ل 3G و3GS
Tutorials:

iPhone 3G (Windows)
iPhone 3GS (Windows)