Thanks to support at dbvis dot com for advice and support.
The problem is resolved.
DBVisualizer SSL connections to DB2 works fine with JRE7 1.7.0_02 on both x64 and x86 environments, when properly configured.
The solution is:
(1) For JRE7 only, ignore one detail of IBM's advice for SunJSSE
at this URL:
http://publib.boulder.ibm.com/infocenter/db2luw/v9/topic/com.ibm.db2.udb.apdv.java.doc/doc/t0054066.htm
For JRE7 with SunJSSE ,do
not add these 2 lines to java.security:
ssl.SocketFactory.provider=com.sun.net.ssl.internal.ssl.SSLSocketFactoryImpl
ssl.ServerSocketFactory.provider=com.sun.net.ssl.internal.ssl.SSLServerSocketFactoryImpl
( Note: these two lines work with JRE6 only, but they break JRE7 1.7.0_02 b13 at least).
(2) Add a driver property sslConnection=true to the DBVisualiser connection.
(3) If you are using the default cacerts file that comes with the JRE7, there's no need for any system property or driver property to identify it. If you specify a "javax.net.ssl.trustStore" driver-property, then ensure the filename is fully qualified (else you may get exception "the trustAnchors parameter must be non-empty" ).
If you are using your own truststore (not cacerts), and/or a non-default password then give relevant driver properties to DBbvisualiser on the connection.