I tried to update my software from iOS 5.0.1 to 5.1.1, but always failed.
I tried to update my device through iPad itself and iTunes but nothing change, failed.
Maybe this will help:
Download the update from here:
The links are straight to Apple servers; make sure you pick the correct file for your device
Connect to iTunes; Hold Option (Mac) or Shift (Windows) and click the Update button. A dialog will open allowing you to select the file you downloaded.
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