I have this same problem importing my Thawte freemail cert. Also, kmail, doesn't seem to check the status of certs that other people sign their email with even if I have their public cert imported into kleopatra. I am running up to date ubuntu dapper 6.06.1 LTS with the latest KDE 3.5.5 packages.
-- importing .p12 certificate fails with "decryption failed" dialog https://launchpad.net/bugs/71791 -- kubuntu-bugs mailing list kubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/kubuntu-bugs