This is reproducible with tiger build 1.5.0-beta-b09 (I haven't regressed
it further).

Run SwingSet2 on solaris or linux with gnububble (?) being the default GTK
theme, choose GTK L&F in SwingSet, go to FileDialog tab, open any of the
dialogs, and drag the divider. Note that the handle on the divider leaves
garbage pixels when dragged.
The same can be reproduced on JSplitPane tab with continious layout
turned off.

My .gtkrc-2.0 file:
#>cat .gtkrc-2.0
# swing.pixmap.smoothScaling
include "/net/jano/export/disk09/swing/themes/pixmap/gnububble/gtk-2.0/gtkrc"

###@###.### 2003-07-07