Im no expert but ill explain the best i can....Tiny Umbrella is a program from someone in the Dev team i believe that allows you to save your iphone blobs so that if you ever accidently upgrade to a version that is not jailbreakable you can downgrade to a version u have saved through tiny umbrella. you can currently save 4.0.1 so i suggest searching google and finding the program and saving them. Its really easy to use, you just hook your phone up and hit one button.
Question....I have 4.0 saved and now i am jailbroken on 4.0.1.....I cant seem to save my 4.0.1 blobs as it is giving me an error message.....has anyone saved blobs off a jailbroken iphone and if so do you do anything differently?