this may solve the problem..
Khanx, the same thing happened to me after I resetted my network settings.
But I managed to perform the JB and now I can use my iphone again.
What you should try to do is to connect the iphone to your computer and start blackra1n, make sure that after it reboots itself blackrain starts automatically again. if it does leave it like that for the night, but make sure you have the sound on, beacause mine finally came out from the loop with only 5 % of battery left.
so its imortant that you can hear when it comes out and start the recharge, if it closes again you may get stuck in same problem again..(for some reason it wont recharge when its connected to you computer during the loop mode)
my only problem is that my wifi is now greyed out...