if u have had any trouble retoring to a custom 3.1.3 firmware and blacksnow on cydia is not working,and it gets frozen after installing blacksnow, here is the solution.

after u restore to CUSTOM 3.1.3 (use pwnagetool on a mac, u can then transfer the custom ipsw to windows to restore if needed)
go to cydia, and add source [Only registered and activated users can see links. ]. from there install the blacksnow rc2 final. u will have unlock and wifi will work too. no need to install another push fix.

not my work, found some info and thot i would pass it along.

also it has been reported that 3.1.3 bootrom exploit has been found, confirmed by a dev-team member. so looks like we are all anxiously waiting for the release after 6-24 release of the iphone 4 and os 4.0. im sure dev-team will do their testing on the new o.s. with this new exploit before releasing it