File Problem

Hi all, I have a suse 9.1 server that runs vsftpd and smb. I have a W2K application that write a lot of video files in this server trhu the ftp and check the files using smb. Well, after a couple of weeks working fine I'm starting to get corrupted files. The original file is ok, but the linux file has some parts that are filled with zeros. The final file size is the same on both system and I didn't find any strange message in the /var/log/messages file. Is there any help someone could give?? Thanks, Diego