I'm using xubuntu edgy with xfce4.4 beta2 and thunar 0.3.2beta2.
I've reported what happens and attached a gdb backtrace on the ubuntu BTS: https://launchpad.net/distros/ubuntu/+source/thunar/+bug/52875
*** Bug 2029 has been marked as a duplicate of this bug. ***
Removing the ~/.config/Thunar dirs fixes the bug.
(I've upgraded from 0.3.0+r21789 to beta2 before getting this bug)
The bug is not really related to an old config, but one of the associated libraries (pango, gtk+, gdk, atk, gconf) is misusing the slice allocator (freeing invalid memory). You can try to run with G_SLICE=always-malloc and set malloc(3) debugging options to trace the source of the problem.
Moving to 0.4.0rc1.
I've just tried to reproduce the bug, but I can't. I guess that the buggy lib against which thunar was linked has been fixed in ubuntu. I'll try again to reproduce, but I'm not sure at all that the bug will happen again.
Reopen if it appears again.