Turn off DEBUG MODE on Optio S40.

I've just bought an Optio S40 which was sold to me as new from the store but it had actually been repaired (inside swapped for new)

I turn on the camera and it automatically goes into a 'debug mode', probably used for testing the camera and left on accidently by an engineer.

Does anyone know how to revert the camera to normal mode? (I imagine it's a special combination of keys?)

Which country do you live in? You should have consumer rights, take it back and demand a brand new one.

I would tend to agree - take it back for a replacement. If an item is sold to you as being new, then it should be new.

If you have a new pentax digital camera, the first time you switch it on it should go into the set up screen to set the date and time. If it doesn't, it's been switched on before!