iPod touch Can't update iPod 3 G after it was jailbroken?

[unkn0w3d.us3r]

Can somebody help me?

A couple months ago, my iPod was jailbroken.
But I told that it was to slow, so i restored my iPod

But yesterday I wanted to update my iPod again(when it was already unjailbroken) to iOS 5 but I coundn't.
It said: Your iPod is up to date your version with you are using is the latest software (4.2.1).

I tried several times on diverent computers and diffrent types of iTunes but I cound't update it...

Can somebody help me please?

 

[Nyy8]

Is your iPod a 8GB? If so, the iPod Touch 8GB is NOT a 3rd generation. There was no 8GB of the iPod touch. It is still running 2nd gen hardware.