Runtime Error with new WAR Deployment - java.lang.verifyError

[Tony Moses]

I am developing a J2EE app on iAS (Sun ONE) 6.0. I am getting the following error when I try to execute the following line of code:
fillClass = Class.forName(fillClassName);
where fillClassName = xxx/xxx/xxx
java.lang.VeryifyError (class: xxx/xxx/xxx, method: xxxx) Incompatible object argument for function call
The weird thing is that the method referenced in the error isn't even being called.
This error was not occuring until I rebuilt my WAR file to contain all of my java packages/libraries (common components and app specific libraries due to customer requirement). I have read that I need to use javac to prevent this from occuring, but that is waht I do use to compile all of my classes. Can anybody provide any insight as to why this is happening?
When I had my jars referenced in the classpath this error was not occurring.

[Michael Ernest]

I've seen this occur when the class in question was available in more than one JAR, particularly when two versions of the same JAR were in the classpath. I'm not aware of a compiler switch that has anything to do with it.