Comment 13 for bug 118304

    This didn't happen to me in a couple of Ubuntu releases, but upgrading
    to Maverick (stardict-gnome 3.0.1-7) introduced it here.

Probably you changed theme, or image for the panel

    I just checked with "strace -f -e open -o /tmp/star.out stardict" that only the icons from /usr/share/stardict/pixmaps/ are loaded.
    Viewing these icons with eog or another tool shows them transparent, but in the notification area I get that light grey background just like in the screenshot linked above. To verify that the icons don't suffer from some obscure format error, I replaced one of them (after backing it up) with a knowingly working one:

    cp /usr/share/icons/hicolor/24x24/apps/updates-notifier.png
    /usr/share/stardict/pixmaps/docklet_stop.png

    The result is the update notifier icon on a light grey background. So
    the problem must be the way the icons are displayed, not the icons
    themself.

Yes, system theme color is being used, to create icon background.
This is the original bugfix regarding white background of notification area icon

http://www.stardict.org/forum/viewtopic.php?f=5&t=246

Try using system theme as panel background.
(right click > properties > background > none)

The only way i found to use a different panel background icon without this issue,
is to recompile stardict using as notification area icon, a custom one with proper background
(you can create it, using original stardict icon and your actual panel background)