This sounds a lot like bug 1243636. Are you using 32 bit Ubuntu? You can check that next to "OS type" label from Details panel of System Settings.
** Changed in: ubuntu Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1244710 Title: encryption on /home/$USER now silently truncates large files To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+bug/1244710/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs