[Arran]

Gluing up that sort of crack never holds over the long term, because wood tends to expand and contract with changes in humidity it will only crack again. I say this from experience, and concur with what Kirk said, the only way to permanently repair it is to replace the damaged veneer. However this is not all bad news, in looking at the pictures of your cabinet I believe that you could repair it by cutting out a strip of veneer as wide as the damaged area, parallel to the grain of the wood, and replace only the damaged sections. The main issue will be finding French walnut veneer with a similar grain and colour to the original veneer next to it, I believe it was quarter sawn. In some cases they also book matched the veneer on one side of the cabinet to the other, I don't know if they would have bothered on this cabinet but on the higher end ones they would have. One good thing about the design of this cabinet is that you would not have to take it apart to repair it, the ends of the veneer meet up with a straight and exposed edge rather then being hidden behind a piece of moulding or terminating inside a dado joint.
Regards
Arran