shell

are you unpacking the .tar.gz file on the same platform it was made on? there are some differences between older Unix versions of tar, such as the non-GNU versions of tar that have shipped with Solaris, and the GNU tar that ships with Linux, etc. If you're going to unpack an archive with GNU tar, it's best to create it with GNU tar.

how does your system look for disk space? was the disk full when you made the archive, or is it full as you attempt to unpack it?

did you create the archive with a cron job? without output redirection, cron can do funky things to archives due to limitations in the size of output it will allow to STDOUT. If you're making an archive in cron, and you're using -v with tar, try redirecting STDOUT to a file, and STDERR, too. See if that helps. tar -cvf archive.tar.gz /path/ 1>archive.stdout.log 2>archive.stderr.log or something like that.