Double-clicking with nothing highlighted yields wrong character

One method of transferring a character into the "Text to Copy" box is supposed to be double clicking on the character.
This method is the most intuitive, as double-clicking is how one selects many things - icons on the desktop, directories or files in the file manager, etc.

However, when I double click on a character, normally I get a different character than I wanted.
Why?
The first click changes the display so that the row that the clicked character occupies is now moved to the top row in the display window.
The mouse pointer is now pointing at the character x rows down from the desired character, x being the number of rows that the display had to scroll to take the desired character to the top row.
When the second click occurs, the character under the mouse pointer is the character that is sent to the "Text to Copy" box.

At this point, the desired character is HIGHLIGHTED.
Double-clicking NOW on a new character, no matter the position, does NOT move the display of characters, and the correct new character is copied to the "Text to Copy" box.

If you remove the highlighting (for instance, click in the "Text to Copy" box), then the problem is back.

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scott@scott-Asus-M2N68-AM-Plus:~$ uname -a
Linux scott-Asus-M2N68-AM-Plus 3.2.0-54-generic-tuxonice #82~ppa1-Ubuntu SMP Sat Sep 28 10:27:12 UTC 2013 i686 athlon i386 GNU/Linux

scott@scott-Asus-M2N68-AM-Plus:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04.3 LTS
Release: 12.04
Codename: precise
[Actually, this is Lubuntu]

GNOME Character Map
3.4.1.1
Based on the Unicode Character Database 6.1.0