iPad 2 - no software update button help!

Well, you are definitely having troubles. So, if I may suggest an alternative way. Go to this link we have here of official Apple firmware and pick the iOS 5.1 version for your device: http://www.ipadforums.net/showthread.php?t=24939. Download it and see if the download finishes. If it successfully downloads, remember where you put it. Oh, and if you are using Internet Explorere, it will try to download the file as a .zip file. If that happens, change the extension to .ipsw (and whatever you do, don't unzip it!).

Or, don't use Internet Explorer ...

Then, after a successful download, connect your iPad to iTunes. It should tell you that your iPad needs upgrading. Accept that message. Then, you should have the main iTunes screen showing with a big old Restore button right there in the middle.

Before you press that restore button, hold down the Shift key and then click on the button. You should get a browser window that'll open and you'll be able to browse to/find the .ipsw file you just downloaded. Click on it and then let iTunes start it's magic - it should go normally from there.

Sometimes, there's a delay in connecting to Apple's computers, which is why it's easier to get the firmware from another place, then let iTunes do the restore ( instead of having it try to do both steps).

That should do it for you to successfully upgrade to iOS 5.1. Give that a try and let us know how you get on. Good luck.

Marilyn