This issue is now fixed by the Need for Speed: Carbon SAVEGAME VALIDATOR v1.00 (see gamecopyworld). However
The current version is VERY buggy as you need the default My Documents location (else you get Run-Time error '5' messages) and it can only be used on a pc with NFSC installed else nothing can be entered.... The NFSC Savegame Selector from
http://www.nfszone.com/NFS_Carbon/Downloads/Savegame (command line, but can handle the alternative mydoc locations, source available) or the sivin's pro saver (also very buggy)
http://sivin.borec.cz/sivin-pro-saver-nfs-carbon