3Gs won't jb with custom ipsw but will after

[bruinsrme]

I waited patiently for the 3Gs jb on 3.1.2 like everyone else.
s we know blackra1n came out first so I gave in and used Geohots program. After a number of hours trying to get it to work I ended up switch machines and it worked right away.
When, the 3.1.2 custom pwnage fw became available for windows users I restored and tried to jb a number of times with the custom ipsw but never succeeded. After I re-jailbroke with blackra1n, no issues. Out of curiousity I tried jb/restore with a custom ipsw with blackra1n installed, and it worked perfectly.

I have tried different ipsws and the results are the same.

why can I jb using a custom only after blackra1n is installed?

TIA
Scott

 

[Night Spring]

Pwnage Tool 3.1.2 only worked on already jailbroken 3GS to jailbroken 3.1.2, and was intended for people on jailbroken 3.0 or 3.0.1 to upgrade to 3.1.2 while staying jailbroken. Therefore your phone had to be already jailbroken (in your case by blackra1n) for it to accept the custom ipsw created by Pwnage 3.1.2. If you get a custom ipsw created with Pwnage 3.1.4, I understand you can use that to jailbreak a 3GS on stock firmware. But for what it's worth, if blackra1n works for you, I haven't heard of any advantage to re-jailbreaking with Pwnage.