~S~
If I remember rightly some of the RAF662 multiswap missions (pinball variations, etc.) were very fussy about which aircraft needed to be available in order for them to both install and run properly.
It may be you lack the aircraft designated as the 'player' in the mission file, or that you have the aircraft and it is lacking a panel or proper sound alias.
If you could let us know which mission it is, I'm sure there are people here who can help. I can't do much more at the moment as I'm afraid the knowledge required is not at my fingertips - I'd need to go and check on some of my game files and while I have been known to spend an honest hour or two cruising the Simviation forums while at work (ahem), I have stopped short of actually installing CFS1 on my office computer...
~S~
Pads