The latest update of Java broke jps and jconsole when Java is launched specifying "-Djava.io.tmpdir" with a value of anything other than $TMPDIR. This affects Virgo and Tomcat.
The problem was introduced in Java 6 update 21 and is fixed by bug sunbug 7009828 in Java 6 update 25.
A workaround for Virgo is as follows. On Mac and Linux to delete the following line in dmk.sh:
-Djava.io.tmpdir=$TMP_DIR \and on Windows to delete the following line in dmk.bat:
set KERNEL_JAVA_PARMS=%KERNEL_JAVA_PARMS% -Djava.io.tmpdir="%TMP_DIR%"