spwolf is probably right about the binary file issue.
Brad: I suspect your files may have been transferred as text instead of binary (binary mode leaves the files intact and does not attempt translation), during either upload, download, or both.
If the issue is indeed a binary/ascii conversion issue, the file might be repairable if you reverse operation, though I cannot confirm. Also, an FTP client called “32bit FTP” claims to be able to solve such problems. I have not tried it; therefore I cannot confirm or deny their claims. Neither the makers of PowerArchiver nor myself endorse “32bit FTP”; therefore, proceed at your own risk.
Lastly, be sure to backup whatever you have already transfered to your FTP server before proceeding, as the files may be recoverable, and I’m assuming the last thing you’d want is to corrupt them further.
Take care