Okay, so having bought the brother-in-law an A710IS for his birthday we visit his hometown for Easter (we live 600km away) and present him with said camera.
At the shop at home I'd said to the sales guy that it wasn't for me and there was little point showing me how to use it.
Well, to cut a long story short, niether of us could open the battery cover. Reads manual in desperation and still couldn't open it. Puts camera back in box intending to phone the Camera shop in the morning.
Then along comes the missus who asks what is wrong - we explain we can't get the batteries in, and she proceeds to open the battery cover & fit batteries.
Not sure which was funnier, us incompetants, or the ease of which the job is actually accomplished. 
Glad you got it figured out, sometimes the simplest things can be the most complicated! 
