REGRESSION: Testcase 4890345 is failing with 50u6_b3 but passing with 50u6_b2

bug4890345.java and Test4890345.java testcases are failing with 50u6_b3 but passing with 50u6_b2.

Testcases failing are,
<Workspace>/workspace_150/test/CTE_REGTEST/Generic/4890345/Test4890345.java
<Workspace>/workspace_150/test/javax/swing/JComboBox/4890345/bug4890345.java

JDK:
---
java -version
java version "1.5.0_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_06-b03)
Java HotSpot(TM) Client VM (build 1.5.0_06-b03, mixed mode, sharing)

Operating System: Windows 2003 SE
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1. Steps to reproduce for Test4890345:
=====================================

Testcase location:
------------------ /net/urts071.india/export6/testSuites/Regression/workspace_150/test/CTE_REGTEST/Generic/4890345/Test4890345.java

1) Copy the 4890345 directory from the given location : /net/urts071.india/export6/testSuites/Regression/workspace_150/test/CTE_REGTEST/Generic/4890345

2) Go to that directory

2) compile all java files
<jdk location>/jdk1.5.0_06/bin/javac Test4890345.java

3) Execute the file Test4890345
<jdk location>/jdk1.5.0_06/bin/java Test4890345


With 1.5.0_06-b03:
==================
Exception in thread "main" java.lang.RuntimeException: Popup was not shown after VK_DOWN key press. Test failed at Test4890345.main(Test4890345.java:86)

With 1.5.0_06-b02:
==================

Popup is shown even after VK_DOWN key press.
Even This test is failing for XP-prof AMD 64 bit jdk.

java -version
=============
java version "1.5.0_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_06-b03)
Java HotSpot(TM) 64-Bit Server VM (build 1.5.0_06-b03, mixed mode)