Cannot find embedded third-party .class in my own signed .cab

Question

Hello,
This is complicated.
I'm building an applet that operates a piece of hardware on a PC (think Win32-only.) A third-party provider (henceforth referred to as TPP) provides software drivers that will be installed on client machines.
ORIGINALLY the TPP provided a <client>.dll and a C/C++ SDK. To make the project work, I followed the article http://www.javaworld.com/javaworld/jw-10-1998/jw-10-apptowin32.html.
I built <homegrown>.DLL using JNI, made a signed <homegrown>.cab, and the applet works just great on IE. However, I have to ditch the entire thing (see below.)
Now the TPP is providing a Java SDK in a <client>.JAR. The SDK interfaces with a <client_jni>.dll.
I can expect that the client machine will have <client>.dll and <client_jni>.dll installed in the \winnt\system32 (or whichever %SYSTEMROOT% directory.)
So, I ditched the <homegrown>.dll, and built a new .cab. Now, to build the .cab, I took the contents of <client>.jar and dumped them into the same directory structure as the one I use to build <homegrown>.cab. Note that <client>.jar is not signed.
So in other words, if you look at the exception below, I, in fact, do have a directory structure that contains: "com/IridianTech/PIDresult.class" and "com/panasonic/authenticam/LoginApplet.class"
When I run the applet, it asks me if I want to run the signed applet. I click Yes. The Java Console responds with the following:
Error loading class: com.IridianTech.PIDresult
java.lang.NoClassDefFoundError
java.lang.ClassNotFoundException: com.IridianTech.PIDresult
     at com/ms/vm/loader/URLClassLoader.loadClass (URLClassLoader.java)
     at java/lang/ClassLoader.loadClassInternal (ClassLoader.java)
     at com/panasonic/authenticam/PIDInterface.<init> (PIDInterface.java:12)
     at com/panasonic/authenticam/LoginApplet.init (LoginApplet.java:52)
     at com/ms/applet/AppletPanel.securedCall0 (AppletPanel.java)
     at com/ms/applet/AppletPanel.securedCall (AppletPanel.java)
     at com/ms/applet/AppletPanel.processSentEvent (AppletPanel.java)
     at com/ms/applet/AppletPanel.processSentEvent (AppletPanel.java)
     at com/ms/applet/AppletPanel.run (AppletPanel.java)
     at java/lang/Thread.run (Thread.java)
I have looked at the contents of <homegrown>.cab with WinZip, and I can see PIDresult.class in the right place.
HOW I AM TESTING: I have IBM Websphere running directly on my PC.
TWO QUESTIONS:
1. Do I need to sign the applet anymore, just to use a pre-installed client_jni.dll? (Probably)
2. WHAT DO I DO??

Answer 1

This is some code i'm using:
<applet code="upload.class" archive="upload.jar" codebase="." width="500" height="200">
<!--<param name="codebase" value="."> -->
<param name="cabbase" value="upload.cab">
<param name="button_text" value="Upload via HTTP">
<param name="file_varname" value="filename_value"><!-- where is this for? -->
<param name="upload_url" value="http://10.2.1.133/upload/recieve.php">
</applet>