This bug at least happens on Solaris (CDE) and Linux (KDE) with Java 1.4.0 and various Netscape 6 browsers. It does not happen on Windows, however.

Start the attached FocusTest.html (make sure to change the codebase to the also attached FocusTest.jar). It uses Java Plug-in 1.4 to start the (signed) FocusTest applet. Prior to running the applet, the Plug-in opens a security warning dialog, which you have to exit via "Grant this session" or "Grant always". After this dialog has been closed, the applet gains no keyboard focus (you cannot type anything into the applet's JTextArea). If you one exit the security dialog via "Grant always" the dialog will not open on subsequent starts of FocusTest, and the applet's JTextArea will then work fine (i.e., it has the focus right after start, shows a caret, and accepts keyboard input).

Note that the problem does not occur if you use a plain AWT Applet (with a TextArea) component instead of a Swing JApplet (with a JTextArea).

The situation where I discovered the bug was with the Sun ONE Webtop's Productivity Applet (aka jclient) that is a singed applet that somewhat behaves like a JTextArea---it is a custom-drawn JComponent that wants to gain focus and accepts user input via keyboard/mouse. It does not operate properly after the Plug-in's security dialog was up.