Java General Exception Errors and Plugins

I'm trying to troubleshoot the cause of the following errors:

basic: Registered modality listener
basic: Referencing classloader: sun.plugin.ClassLoaderInfo@a6aeed, 
refcount=1
basic: Added progress listener: sun.plugin.util.GrayBoxPainter@af8358
basic: Loading applet ...
basic: Initializing applet ...
basic: Starting applet ...
network: Connecting http://www.java.com/jsp_utils/JavaCallJS.class with 
proxy=DIRECT
network: Connecting http://www.java.com/jsp_utils/JavaCallJS/class.class 
with proxy=DIRECT
load: class JavaCallJS.class not found.
java.lang.ClassNotFoundException: JavaCallJS.class
	at sun.applet.AppletClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.applet.AppletClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.applet.AppletClassLoader.loadCode(Unknown Source)
	at sun.applet.AppletPanel.createApplet(Unknown Source)
	at sun.plugin.AppletViewer.createApplet(Unknown Source)
	at sun.applet.AppletPanel.runLoader(Unknown Source)
	at sun.applet.AppletPanel.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.io.IOException: open HTTP connection failed.
	at sun.applet.AppletClassLoader.getBytes(Unknown Source)
	at sun.applet.AppletClassLoader.access$100(Unknown Source)
	at sun.applet.AppletClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	... 10 more
basic: Exception: java.lang.ClassNotFoundException: JavaCallJS.class

The error that has caught my eye is "open HTTP connection failed".  I 
have local Java apps (Eclipse IDE, Unlimited FTP) that run fine but 
can't access the internet.  But applets don't run - just generate errors 
like above.  Turns out that there are no Java related plugins in the 
Firefox plugins directory.  I've got Quicktime and Flash related files 
there, but nothing Java related.  If I try to install JRE 5, it tells me 
that it's already installed.  Yet applets (e.g. www.java.com) cause 
General Exception Errors and I still have no Java related files in my 
plugins directory.

Anybody have ideas as to the cause of this?  Coudl somebody tell me 
which files need to be in the plugins directory?  Maybe I can just copy 
them there myself.

Thx
-K2