Redsn0w currently only offers a tethered jailbreak. Meaning each time you need to reboot your phone you will have to do so using redsn0w. What you want to do now is plug your phone into the usb port, open redsnow, browse for the OS just like you did when you jailbroke the first time, let it process, hit next, and it will patch the kernal, then unclick the box next to install cydia and click the box next to just boot tethered, then you will have to turn your phone off and put it into DFU mode just like you did when you jailbroke, then your phone will boot up. Until an untethered JB comes out this is how you will have to boot your phone.