Larger Videos no longer play when stored in my WordPress directory

Hi,
Over the weekend, a problem has somehow arisen.
flv videos larger than 25 mb stored in my WordPress directory will no longer play. If I move the video to a different directory outside of the WordPress directory, it does play. Before this weekend, those videos were playing.

Details:
(1) These large videos were uploaded via ftp.
(2) I use the most recent Flowplayer plugin. But I know the issue is not with Flowplayer because when I change the video to a different directory outside WordPress, the video will play within the Flowplayer player.

Can anyone tell me what might have happened?

Thanks,
Mike