The point of this thread was to establish whether anyone had ever migrated code from java 1.4 to 1.6 and weblogic 8.1 to weblogic 10.3 and experienced differences in functionality.
I tested the application on the environment running java 1.4 and weblogic 8.1 and the functionality there is ok.
I then tested the same application on the new environment running java 1.6 and weblogic 10.3 and the functionality was different.
The reason I did not elaborate on the errors and exceptions picked up is because they have not really been related to the functionality I was testing and because there aren't really any differences in the logs from the two instances of the app.
What I wanted to establish was whether a migration from Java 1.4 to 1.6/Weblogic 8.1 to 10.3 without any code changes could cause differences in functionality or if anyone had ever experienced a similar problem.