Update 2012-02-28: Consider upgrading to BackupPC 3.2.0 to resolve this.
We recently upgraded our BackupPC servers to BackupPC 3.1.0 on Ubuntu 10.04 Lucid Lynx. It’s working almost perfectly. However, the “Download ZIP archive” restore option no longer works. This is due to a bug in recent version of the Archive::Zip Perl module which generates corrupt ZIP archives.