Then the device is currently in recovery mode. This means that the software or hardware of the device has been corrupted or damaged and needs restored. Connect the device to iTunes and restore it to gain access to the device. Keep in mind that this will erase all of your data that was currently on the device. For more information or assistance with the issue you can take the device to an Apple Retail Store or contact AppleCare at 1-800-692-7753. Hope this helps.
My iphone frozen on screen with itunes USB cable
Do what the icon says, connect your phone to the last computer you synced with and it should restore. If it doesn't follow the procedure in http://support.apple.com/kb/HT1808