I used to get that message, when i have a slow connection (56k dialup) and can hardly download the file. first remove the file, and then download the file again (i don't recommend uploading the .tar.gz from FTP clients, instead, downlaod it from your shell promtp)
next do,
tar -zxvf anope-1.7.14.tar.gzthis is how i used to do and works fine for me on FreeBSD