Can you jailbreak your ipod touch after you alreday unjailbroke it?

i jailbroke my ipod touch 4g 4.2.1 using greenpois0n. i downloaded somethin from cydia and it screwed it up in a bunch of different ways. i went on itunes and restored my ipod. it also upgraded it to 4.3.3. when i used greenpoison again after it turned white it said unable to find something four times. do i need to use a different way of jailbreaking it? will it turn back to its way that it was before i restored? will it turn into a brik? PLEASE ANSWER!!!!!