do they play together on the same game? Or have they done?
We all use the same disc, but all four of us have our own profile and seperate saved games.
Do they have their own profiles with biometric identitites setup?
Yes
Do you have more than one memory location for the save, for example a memory card and a hard drive?
No, just the hard drive that came with the Xbox 360 Elite (12 months old)
Do the profiles have other saves (from different games) that you can check?
Two of the profiles were created in order to play with the Kinect. I don't think any of our other Kinect games require saved profiles (Joy Ride, Adventure), but I will check.
Since this problem occured have they started a new game?
Yes and no. They haven't chosen to start a new game, but when they chose "continue" a new game started (i.e. they arrived on teh island and had to go through the introduction stuff).