Kbackup for KDE works great to back up to an external Samba drive, whereas Keep which comes with Kubuntu gives error messages. Get rid of Keep, and install Kbackup. A .deb package is available here.
KBackup is a program that lets you back up any directories or files, whereby it uses an easy to use directory tree to select the things to back up.The program was designed to be very simple in its use so that it can be used by non-computer experts.The storage format is the well known TAR format, whereby the data is still stored in compressed format (bzip2 or gzip).
The backup can be put onto a local directory (mounted device, etc.) but also on a remote URL (thanks to KDE KIO).
It also includes a german, french, italian, slovak, portuguese, swedish and russian translation for the user interface and an english, french, russian and german handbook.
You’ll find all RPMs including 64bit versions for different distributions on the openSuse build service (links below)
NOTE:Due to a KDE3 limitation, it can only backup files each up to 4GB in size (on 32bit platforms at least; therefore larger files are skipped)