executable jar encountering exceptions in 1 server but not the other

Hi all,

I have a standalone application (executable jar) in the production environment.
Some exceptions were thrown stating that it cannot find certain class files, but the class files have been placed in the jar file before running it.

I managed to get the production copy and place it in the UAT environment to test (different server) with the same data and to my surprise, no exceptions were thrown at all.

Could it be due to some caching problem?

Thanks for any advice,
Atiz