itunes update crashed my iphone 4

I plugged my  phone in to sync and it prompted me to upgrade to IOS 6.xxx. Then my computer flashed a notice saying that itunes could not upgrade. Now my phone is frozen, with an itunes logo and a usb plug on the screen. I tried a hard boot on my phone, and I closed itunes on my computer, then tried again. itunes doesn't even see my phone, so I can't even restore. Please help.