When filling in forms, sometimes the keyboard is lost, no data can be entered into text fields. This usually happens following selection from a long popup like a full country selector (UK usually at the end and several pop windows needed to get to it)
It's an interaction between netscape, motif, and your window manager. You'll need to select another window, and re-select the netscape window. *** This bug has been marked as a duplicate of 6409 ***