Apparently they did not try installing the game at the store to prove or disprove a problem with the CD key?
In the North American and UK English versions, the copy protection can produce a report which can be used to generate a key to allow the game to be played on that specific computer, in cases where there is a conflict with the optical drive (causing the play CD not to be recognized). Is there any such option in the French version?
Try contacting the publisher (it is possible some CDs and cases got mixed up between batches, so the listed CD key is not for the CD you have), or email Larian (support@larian.com).
