Signed Applet mix code under J7u21or J7u40 gives java.lang.NoClassDefFoundError

Signed Applet mix code under J7u21or J7u40 gives
java.lang.NoClassDefFoundError

Please be aware this has been posted on Oracle Java Forum at
https://forums.oracle.com/thread/2577877
I have a simple applet which shows a graph; this applet has two jar file,
the main jar file is signed by a trusted CA and the other jar file is
unsigned
in the manifest for the signed jar file, I have added
Trusted-Library value="true"
Whe applet starts from the java console when it tries to invoke a create
object on the class from the unsigned jar file, I get
java.lang.ClassNotFoundException for the given class from the unsigned
jar.
I have tried this on window 7 Chrome and Internet explorer based on
variety of Java 7 release (40, 21 on internet explorer and release 6 on
Chrome)
It does not work.
If I signed the second jar file, it works fine.
Please notice, I do not want to bypass the check for mix code from java
configuration.
Any idea or hint will be highly apprecieated.