IP - Exception Error of type CX_SY_REF_IS_INITIAL

Has anyone encountered the following situation and if so how did you overcome it?

I am using BI-IP to run some planning scenarios. I have 2 workbooks which are set up in a similar fashion. In one of the workbooks I use a button to execute a copy function. It works perfectly fine. On the 2nd workbook though I have the same function/button setup and any time I execute the function I get the following error,

"An exception with the type CX_SY_REF_IS_INITIAL occurred, but was neither handled locally, nor declared in a RAISING clause"

and I get disconnected from the system. Other planning functions connected to buttons work just fine on this workbook so I don't think the workbook is corrupt.