Ensure that the jre package you built was installed. It might not be. Your symbolic links won't work if the plugin isn't there.
$ pkg_info | grep jre
You can use pkg_add or you can use make install with the SUBPACKAGE environment variable, as you prefer:
# cd /usr/ports/packages/<arch>/all
# pkg_add jre
or
# cd /usr/ports/devel/jdk/1.5
# env SUBPACKAGE=-jre make install
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