Hold down the power and home button for as long as it takes to have the apple logo show up then your good but if it shows the iTunes recovery wallpaper logo thing then download iReb R5 from here [ Register or Signin to view external links. ] then click on the second tab in iReb (be sure to run as an administrator if on windows, Mac just run reggularly) the tab should be call restore recovery loops or something like that the click on restore recovery mode loops and soon your problem should be fixed. Hope I helped.

This TuT works great if you're stuck in DFU mode still.



and

This TuT is great if you're in a bricked state. (3G or 3GS)

If the above option doesn't work, try re-jailbreaking it. I've been stuck in DFU mode several different times and re-jailbreaking has worked each time. (Along with holding Home+power buttons for 10-15 seconds until the Apple logo appears.

when mine does this i do the thing to put into dfu mode but it takes it out and comes out and apple logo comes up

download recboot....