This was tested with Xconfigurator-4.3.38-1 from http://people.redhat.com/teg/xc/. The monitor list is so wide that it exceeds the "window" frame. While not a critical bug it sure makes Xconfigurator look a little less "polished".
Not reproducible at all - there's even a good margin.
I might have phrased that poorly. Please try if you can reproduce this using LANG=sv_SE (that's what I used). The longest strings in the monitor window aren't translated though, so I don't think it's the translation that causes the problem. Also, what I meant wasn't that the list exceeded the window, but rather that it is so wide that the "window" line border to the right of the list gets messed up. Watch it carefully... ;-)
OK, that gave a clue. One of the monitor entries had a tab in it - fixed in CVS. Very good spotting.
Fix confirmed in Xconfigurator 4.3.40. We're working fast today :-) Closing this.