Created attachment 2176 screenshot sometimes thunar uses a different (wrong, much too big) font size than the other xfce applications. attached is a screenshot from desktop, you'll notice the difference of the menus in thunar and e.g. the terminal. please ignore the black box in the lower right corner, I'm using a dual display setup. I've got no idea how to isolate the bug but I'm willing to try if someone gives me directions how to proceed. I'm running xfce 4.4.3 with thunar 0.9.3 on i686 Arch Linux. As far as I can tell its pretty vanilla upstream source.
Thunar uses GTk for this and has nothing custom. Most likely the dpi on your system is not correct or system font, while the terminal font is smaller (a font you _can_ override).