If you can verify that the error is indeed ENOSPC with,

use Errno;
warn "Yes, it's ENOSPC\n" if ENOSPC == 0+$!;
[download]

then you are definitely running out of drive space. Perhaps you have plenty on the system, but you could be running out or hitting a quota on the particular fs you're writing to.

This would be easier to diagnose if you showed code.