Working with mp4 and m4v file

I am working with .m4v file that came from a Mac computer.

I then renamed it .mp4 and was able to import it into Flash CS4.

Note that this file was imported into Flash CS4 on Windows XP with Service Pack 2.

I then export the file as swf. But when viewing on the Mac and Windows Vista the page is completely blank even when the file is saved as CS3 but it plays fine on the Windows XP machine.

Anyone help appreciated.

Thanks
Dave