If you drag a file that isn't a comp (eg. an image file) to Fusion's title bar, menus, main toolbar or comp tabs (ie. any area you can drag a comp to load it) then Fusion attempts to load that file as a comp and will give that error when it turns out to not be a comp.
If it is supposed to be a composition, there might be something odd on line 40. Just open it up and check. I've never seen something like that, but your composition might actually be corrupted.