The following is the report from SAP AG development.
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Summary:

CJK Unified Ext B characters in text of Swing UIs are not displayed
(blank square) using "Dialog" font.

Steps to Reproduce:
Run attached program:
java -cp CJKUnifiedExtB.jar CJKUnifiedExtB.CJKUnifiedExtB
The jar contains both .class and .java file. The character in the sample
is U+23F80.

First line displays the correct character as a png for comparison.
Second line displays the character on JLabel and JTextEdit using
"Dialog" font.
Third line displays the same, but using "PMingLiU-ExtB" font.
(Please change the "native" font in the sample according to the

availablity of appropriate fonts in your environment.)

Expected Results:
JLabel and JTextEdit should display the same correct character both with
"Dialog" and the "native" font.

Actual Results:
JLabel with "Dialog": blank square
JTextEdit with "Dialog": blank square
JLabel with native font: correct character
JTextEdit with native font: correct character

Regression:
Happens both with JSE 5 and 6 on Windows Vista Enterprise, other Windows
versions and OSes might be affected as well.

Choosing a native font is not a helpful workaround for a Unicode
environment, since it causes characters from other languages/scripts not
being displayed. We have customers with Unicode environments requiring
this working with "Dialog" font.
One of them has a Unicode project on hold because of this, therefore the
high prio.
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