FADE is a copy protection software feature incorporated into OFP. If you're getting this message, OFP is under the assumption that you are not running a legitimate copy of OFP. FADE can make playing OFP extremely annoying or absolutely not worthwhile.
Some owners of legitimate original OFP CDs are afraid that the FADE copy protection scheme might be affecting their copy because they think that some instability issue they have with OFP might be caused by FADE. While BIS is unable to provide exact technical specifications on what FADE is and how it works, they have stated some facts about FADE that might be helpful:
BIS and CM have stated that these are the major aspects of FADE technology and they are triggered by using counterfeit versions of the game, no-CD cracks, trainers or cheats. The solution is to only use the original retail version of OFP as installed from the CD, as well as applying only original upgrades and patches from official OFP web sites.
However, there have been recent complaints by OFP customers with legitimate copies of OFP who are nevertheless getting this message or other symptoms that appear to be FADE related and are unable to play OFP. If you're one of these legitimate customers, contact CM's customer service by email.