If you delete a file, and then copy in another file with the same name, the old file's modification date is shown. For example:

 mkdir -p ~/test/del/ ~/test/keep/
 touch -d 20120103 ~/test/del/foo.txt
 touch -d 20090103 ~/test/keep/foo.txt

Now open a thunar window on each directory. Delete either file, and copy over the other one. The timestamp is "sticky". This isn't reflected at the filesystem level, and the error does not persist after thunar is restarted.

Here is a video demonstrating the bug:

http://youtu.be/9rU_5IUuMqM

This might be related to the other thunar timestamp bugs, but opening a new bug because this is a specific, easily reproducible case.