Description of problem:
Trying to copy a directory from a NTFS partition to a USB stick.
I had two tabs open in Thunar and dragged the directory from the source (WiLishare) to the tab of the destination (257MB Mighty drive)
Error is repeatable! Tried 4 times
I succeeded copying when I switched Thunar in 'Tree mode' (Ctrl-E) for the side pane. Now I opened the source drive in a tab, dragged the directory to the destination in the tree pane. Repeating this operation failed also, so it might not be related to the problem.

Version-Release number of selected component:
Thunar-1.6.4-1.fc20

Additional info:
reporter:       libreport-2.2.3
backtrace_rating: 4
cmdline:        /usr/bin/Thunar file:///run/media/tom/WiLiShare
crash_function: _dbus_message_add_counter_link
executable:     /usr/bin/thunar
kernel:         3.18.6-100.fc20.x86_64
runlevel:       N 5
type:           CCpp
uid:            1002

Truncated backtrace:
Thread no. 1 (10 frames)
 #0 _dbus_message_add_counter_link at dbus-message.c:289
 #1 _dbus_message_add_counter at dbus-message.c:339
 #2 _dbus_transport_queue_messages at dbus-transport.c:1140
 #3 do_reading at dbus-transport-socket.c:883
 #4 socket_do_iteration at dbus-transport-socket.c:1194
 #5 _dbus_transport_do_iteration at dbus-transport.c:976
 #6 _dbus_connection_do_iteration_unlocked at dbus-connection.c:1234
 #7 _dbus_connection_block_pending_call at dbus-connection.c:2415
 #8 dbus_pending_call_block at dbus-pending-call.c:748
 #9 dbus_g_proxy_end_call_internal at dbus-gproxy.c:2399