you can try Ifaith very hit and miss but it's your only chance. it will not preserve your baseband if you mess that up you are sol. btw the iphone hack section is a better place to ask jailbreaking questions.
If you tried ifaith and it didnt work and if you didnt save shsh blobs before then you're sol.
The only shsh blob you will be able to save now is 4.3.5 and above.