When jre version has milestone appended, for example, "1.6.0_10-beta", "1.6.0_10-rc", jre runtime parameters entered in java control panel are not preserved. They are lost when refresh jre list.
To reproduce it, install 1.6.0_10 rc. Check output of "java -version" to make sure the version string has "-rc" in it. And open JCP java panel, make sure the "1.6.0_10-rc" is listed. Enter jvm parameter for "1.6.0_10-rc" in JCP, for example "-Dsun.java2d.noddraw=true". Save it and close JCP. Open JCP again, look the java panel, the jvm parameter is not there.
This is not reproducible if jre version is "1.6.0_10".