FULL PRODUCT VERSION :
java version "1.6.0-rc"
Java(TM) SE Runtime Environment (build 1.6.0-rc-b96)
Java HotSpot(TM) Client VM (build 1.6.0-rc-b96, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows 2000 [Version 5.00.2195]

A DESCRIPTION OF THE PROBLEM :
The code in BasicLookAndFeel initComponentDefaults is:

"ComboBox.ancestorInputMap",
            "ComboBox.isEnterSelectablePopup", Boolean.FALSE,
new UIDefaults.LazyInputMap(new Object[] {
"ESCAPE", "hidePopup",
"PAGE_UP", "pageUpPassThrough",
"PAGE_DOWN", "pageDownPassThrough",
"HOME", "homePassThrough",
"END", "endPassThrough",
"ENTER", "enterPressed"
}),

while it should be

            "ComboBox.isEnterSelectablePopup", Boolean.FALSE,
"ComboBox.ancestorInputMap",
new UIDefaults.LazyInputMap(new Object[] {
"ESCAPE", "hidePopup",
"PAGE_UP", "pageUpPassThrough",
"PAGE_DOWN", "pageDownPassThrough",
"HOME", "homePassThrough",
"END", "endPassThrough",
"ENTER", "enterPressed"
}),

The result is that for *all* third-party LAFs that extend Basic and not Metal, there's a ClassCastException in BasicComboBoxUI.getInputMap since the "ComboBox.ancestorInputMap" points to a string "ComboBox.isEnterSelectablePopup" and not to a InputMap

REGRESSION. Last worked in version mustang


REPRODUCIBILITY :
This bug can be reproduced always.

Release Regression From : mustang
The above release value was the last known release where this
bug was not reproducible. Since then there has been a regression.
The bug is a regression of the 6428549.