FULL PRODUCT VERSION :
java version "1.6.0_03"
Java(TM) SE Runtime Environment (build 1.6.0_03-b05)
Java HotSpot(TM) Server VM (build 1.6.0_03-b05, mixed mode)

=> the same bug when using Java SE 6u5 Binary Snapshot Release

ADDITIONAL OS VERSION INFORMATION :
Ubuntu 7.10 (Gnome version)
Kernel: Linux saringnb 2.6.22-14-generic #1 SMP Sun Oct 14 23:05:12 GMT 2007 i686 GNU/Linux

This bug does not exists on Ubuntu 7.04 and before

EXTRA RELEVANT SYSTEM CONFIGURATION :
Gnome 2.20
GTK+ 2.12
Human GTK Theme (same error with all other GTK themes)

A DESCRIPTION OF THE PROBLEM :
In all applications which are using JComboBox widgets the button right next to the textfield is not drawed, it's missing. The combobox still works, it's a display error.
This happens in all application with JComboBox widgets, e.g. WebStart, NetBeans, ...

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Just start an application with a JComboBox on Ubuntu 7.10, e.g. start "javaws -viewer".

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The button right next to the JComboBox textfied must be visible.
ACTUAL -
The button right next to the JComboBox textfied is missing.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
The following GTK warning are printed to the console when a JComboBox is displayed:

(<unknown>:9650): Gtk-WARNING **: Attempting to add a widget with type GtkButton to a GtkComboBoxEntry (need an instance of GtkEntry or of a subclass)

(<unknown>:9650): Gtk-CRITICAL **: gtk_widget_realize: assertion `GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(<unknown>:9650): Gtk-CRITICAL **: gtk_paint_box: assertion `style->depth == gdk_drawable_get_depth (window)' failed

(<unknown>:9650): Gtk-CRITICAL **: gtk_paint_box: assertion `style->depth == gdk_drawable_get_depth (window)' failed

(<unknown>:9650): Gtk-CRITICAL **: gtk_paint_box: assertion `style->depth == gdk_drawable_get_depth (window)' failed

(<unknown>:9650): Gtk-CRITICAL **: gtk_paint_box: assertion `style->depth == gdk_drawable_get_depth (window)' failed

The same Java version has worked correctly on Ubuntu 7.04, which is using an older GTK library.


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
Not needed, just start e.g. "javaws -viewer".
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Don't know any workaround.