This is jEdit-5.2pre1 with Java 7u55.
The buffer switcher looks a bit odd in various look-and-feels, e.g. Gtk+ on Linux or native Apple on Mac OS X.
With Nimbus (on Linux and Mac OS X) the selected line lacks a visual clue: the color for highlighting is not visible.
Problem solved in #3889.
please assign this ticket to yourself and set the status to closed-fixed.