It has happened to me as well. I started downloading an iso image last night, stopped the download and turned off the pc; now every time I try to resume the download d4x closes unexpectedly, even when trying from console. I sending the bug report.
** Attachment added: "d4x crash when resuming download" http://librarian.launchpad.net/5916672/_usr_bin_d4x.1000.crash -- d4x crashes and closes https://launchpad.net/bugs/66445 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs