Applet throws ClassNotFound exception with cache enabled

builds reproducible - b38 onwards
The bug is not reproducible on b37

OS tested - Win XP Pro, Win XP Home
browsers tested - IE6.0, MZ 1.7.x

Steps to reproduce

1) Install jre1.6.0 b37 or later

2) Delete the folder "java"
C:\Documents and Settings\{User}\Application data\Sun

3) Open Java Control Panel, and enable "Show java console" and "Show Applet Lifecycle Exceptions"

4) Make sure the cache is enabled
General -> Settings ->Temporary Files Settings
"Keep temporary files on my computer" should be checked

4) Open the browser and launch the following applet
http://sqeweb/deployment1/deployment_tiger_exec_ws/deployment/src/plugin/phonehome/applethtml/GrayBoxTest-19.html

5) Only three of the six frames are loaded and ClassNotFound exceptions are thrown in the java console. Please see the attachment for the exceptions thrown

6) Now open the Java Control Panel and disable cache
General -> Settings ->Temporary Files Settings
"Keep temporary files on my computer" should be unchecked

7) Load the above applet again, and the applet loads fine and no exceptions are thrown.

expected behavior - no exceptions should be thrown with cache enabled.