Ipod Touch 3g wont DFU

[frantona]

Hi! I have an ipod touch 3g 16gb wich i just updated to 4.2.1, im trying to jailbreak with greenpoison, but im unable to put it on DFU mode, i follow the instructions but the ipod will just turn on in normal mode... :S

Any clues?

[teej1410]

Make sure iTunes is NOT open. And also, you may need to check your firewall settings and be on the administrator's account.