I have the same bug. No custom themes or anything (& ~/.themes is empty). I installed a fresh version of dapper and upgraded to edgy without using much and problem has happened since.
** Attachment added: "Complete crash report generated by OS" http://librarian.launchpad.net/5360119/_usr_bin_gnome-theme-manager.1000.crash -- gnome-theme-manager hangs, stops updating UI https://launchpad.net/bugs/68578 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs