Originally Posted by gfunkdave

It's still possible to downgrade, but the window will probably end today or tomorrow.

1. Download the version of 5.1.1 appropriate for your device here.

2. Connect your phone to iTunes and put it in DFU mode.

3. When iTunes recognizes the device, hold down Shift and left click the Restore button.

4. Choose the .ipsw file you downloaded.

Be sure you back up your phone first!