As Joost said, FTP can fail often. You may get timeouts on the link or the file on the other end may be locked preventing reads, which is the cause of many FTP failures at my site. I've even had problems with the file being in the wrong mode (ASCII/BINARY/EBCDIC), so now my scripts tend to explicitly choose which one is required for each file.

Just yesterday, I posted a reply with some code regarding Net::FTP use. Perhaps it will be of some use to you. Though you'll probably want to review the whole thread as there were plenty of other helpful answers too.

--roboticus