it could be that the problem lies in the pawn.ini, section [conversation].
If somewhere in that section the file media\bitmaps\conversation\man.bmp is specified then you know whrer the problem lies.
If you want a quick solve you should just make a file called man.bmp in the RF folder subdirectory media\bitmaps\conversation
This may not be most elegant, but it satisfies RF for the first and then if somewhere in the game your bitmap appears, then you know where to search.