PowerShot SD1100 - camera seems to have frozen

Question

It is our first week with the camera. None of the buttons will work other than the take the picture button. Pulled the battery and put back - does not help. Can not view previosly taken photos. The screen says ISO 200 and there is a small green box outlined. Pressing the ISO button (nor any other helps). Is some lock feature engaged? The manual does not seem to help. Thank you.