Most of the places i found in forums was to sign the jacob.jar and frmwebutil.jar.It is not necessary to sign the Oracle provided frmwebutil.jar because it has already been signed by Oracle. However, you do need to sign the jacob.jar but more importantly, what version of the Java Com Bridge did you install? The version you used with Forms 10g is not compatible with Forms 11g. The Java error you are getting suggests to me that you have the wrong jacob.jar version (it should be 1.14 instead of 1.06).
...Plugin2ClassLoader.getPermissions ...What are the permissions on all of the jacob related files and who is the owner of these files?