The file is probably toast and you've lost what it contains. Try opening the authoring environment and execute 'go to "path_to_movie"' from the message window, or open it as a MIAW. If neither of these work you should start again.
In addition to what Sean said, you can try to update the movie using the Xtras, Update Movies menu. Make sure to use the Update option in the next screen that comes up. Sometimes that will help... particularly if you have a newer version of Director, like if your file is in Director 10 and you update to Director 11. But it has fixed problems in same version "updates" as well.
Some operating systems have trouble with very large files, so you may be able to get away with opening that file on a different machine with a different OS. I would highly recommend finding a 64 bit OS on a machine that has >2GB RAM. That would give you the best chance.
For the future, if your file exceeds a few hundred MB, you are doing something wrong. You can separate assets into external casts very easily and make use of other external resources when needed to keep the file size down.
I have also just started getting this problem ( my.dir is only 7Mb );
1 - double-click my.dir icon inside My Documents
2 - director begins to open
3 - dialog boxes pop up requesting location of linked scripts
4 - 'fata error' dialog box
1 - double-click director.exe icon on my desktop
2 - director opens, blank
3 - use director's file/open to navigate-to/open my.dir
4 - dialog boxes pop up requesting location of linked scripts
5 - no problem
this fatal error thing began last night; it followed a very strange runtime error regarding lists, which is a bit too difficult to explain here; the error came out of the blue;
I don't recall my director having been so buggy when I last worked on a director project about 2 years ago; I am thinking that something about my computer may have something to do with it;