iPhone stuck in recovery mode

I'm having the same trouble. It tells me it's in recovery mode and to restore it before I can use it in iTunes. I click restore and after a few seconds another message pops up

"The iPhone could not be restored. An unknown error occurred (21)".

I looked up error code 21 but no explanation was found. I don't think mine even downloaded the new update at all.

this is what is happening to me ): . .

i went in to the o2 shop and they told me to turn my phone of and hold the home button down whilst plugin into itunes, but nothing happened ): ..
maybe you should have a go see if it works for you x

First I would try rebooting the PC if you haven't already. Then, as has been suggested, turn the phone off. While off, hold down the Home button while plugging in the USB cable. Keep holding the button until the graphic to plug into iTunes pops up. Then release the button. See if Windows will recognize it then.

I bought this iphone 3g 16gb in the start of July 2009.
My problem is that, when I connect my iphone to my computer it is showing "Unknown Device". I first thought it to be the problem from my computer. So I used another computer to connect, still same problem. I bought new USB connect cable, still same problem. Other Iphone devices are recognized in my computer.

If I restart my computer while my iphone is plugged in, then it is recognizing and I can sync with itunes.

All this confirms that the error is from the iphone.

Can you please give me suggestion or guidance how to solve this issue?

I've tried all of the above suggestions with no luck. Thanks for the advice though.

Hey Guys,

I'm sure you have this sorted by now, but just in case...I found this link in a different thread and it worked first time. My first day of iPhone4'ness came to a horrible end when I kept getting the error (9) in restore process. I tried different USB cables, iTunes accounts, even some voodoo and nothing worked. Then I stumbled on this and its fixed. I had restored from my old 3Gs and I have a feeling that I will have to restore this iPhone4 as a new phone and start over if its going to work properly.

http://discussions.apple.com/thread.jspa?threadID=2508016&tstart=0

Best of luck.
D