I've found sometimes it took a while for my java fern to adjust to new conditions and that the leaves would develop a lot of brown/black spotting and die right back.
As long as the rhizome itself is still green and healthy looking, your java fern should bounce back. I cut practically all the leaves off one of my java ferns as it had died back and today it is ten times healthier than when I first got it.
Hello LBF. :) In my thread that you posted, you said that some of the plants would die off to let new plants grow, right? My Java Fern seems to be browning a bit. (Still in QT) I know I suck at plants. I should know that by now and they're one of the easiest plants plants to take care of. :\ ~LTB