HELP! Can't update/restore Jailbroken Iphone

[Marky018]

I have an Iphone 4 Jailbroken on 4.2.1 now I want to update the firmware to 4.3.1 and just restore to remove the Jailbreak.

As I try to update/restore on itunes, it tells me give me the following error:
The iphone cannot be updated because the iphone software update server could not be contacted or is temporarily unavailable.

I have tried to update/store on another computer without success.
I have no connection issues to the internet, my OSX and Itunes versions are all up to date.
I have searched many boards for resolutions but none have worked.

Anyone's help is greatly appreciated.

 

[McGiord]

Hold the sleep/wake and home buttons for more than 30 seconds to put in recovery mode. Then connect to iTunes and restore to the firmware that you want to, you can click while holding the option key to browse your Mac and choose the firmware that you want to load.