Shortly after the appearance of pwnagetool 2.0.1 on the Mac, WinPwn has also been upgraded.
If WinPwn closes during IPSW build, have a look at this thread.
ok, it worked. If iTunes refuses to restore your IPSW file, try generating one with a 512 MB partition size. For me, that did it. Now the proud owner of an unlocked, jailbroken 2.0.1 iPhone 2G.