More specifically, when it says:
"iPad Software Update (processing file)"
I get a pop up saying:
"*There was a problem downloading the software for the iPad "iPad". The network connection timed out*. Make sure your network settings are correct and your network connection is active, or try again a later."
And I've tried again later. Didn't work.
Most commonly, this is caused by anti-virus or a software firewall on your desktop interfering with the download.
If you run either or both, try disabling them; if not, or if that doesn't work, download the update file from the link below and use the downloaded file to install the new version.
Connect the iPad, and hold the Alt/Option key (Mac) or Shift key (Windows) while clicking the Update or Restore button. You'll get a dialog allowing you to select the downloaded file
I had the exact same problem. I was clicking the download and update button which would give me the message you received. It worked when I clicked download (only the download button) and let it download. After that, I reconnected my iPad to the computer , clicked update, and it automatically extracted the download and did the update. You may already have this solved on yours but maybe others can benefit. I found this while looking for answers to get mine to update.