Why do JARs made with JBuilder 2006 Enterprise not work outside IDE???

[alan_conoco]

Hi all,

I have written a program in JBuilder 2006 Enterprise (Win NT, JRE 1.5)
which works perfectly within the IDE.

However, when I use JBuilder to create a JAR of my project and then try
to run in from the command line it throws the run-time exception
below...

Exception in thread "main" java.lang.SecurityException: class
"Com.package.MyPackage.MyExcpetion"'s signer information does not match
signer information of other classes in the same package

I have used JARs before but never come across this sort of error, maybe
worth adding that the program uses JavaMail to send emails.

More confusing, why does it work in JBuilder, but not outside?!?

Any help would be greatly appreciated, i am stumped!

A