This is what I have tested/found out...
1. It works without any problems on an Windows NT machine.
2. All of our servers were upgraded at the same time, however three out of the four worked fine, only one had the Java Applet Action Bar trouble.
3. Windows XP seems to be affected, however, we have had reports of Windows 95 and Windows 98 having the same trouble.
One fix seems to be to re-install Internet Explorer 6 on a Windows XP machine.
Another fix seems to be to install the lastest Java Runtime Environment. (
http://java.sun.com/j2se/1.4.2/download.html)
All you need is the JRE, not the SDK.
I'm not sure if this is "the" fix, but it seems to work for us.
Hope this helps...