Management Reporter: Index and length must refer to a location within the string

Hello:

We are on Management Reporter 2012 CU13 with the Legacy Adapter.

Within a column definition, we created a "CALC" column containing an "If, then" formula.  When we ran the report, the column displayed accurate data.  Good!

When we went back into the column definition, afterward, we tried to insert a column to the right of this "CALC" column.  Upon doing so, though, we were kicked out of Report Designer and the following error appeared:

"Index and length must refer to a location within the string."

I have seen two postings here in the Community on this error but no resolution.  Also, I went on CustomerSource for Dynamics GP and none of the service pack fix lists address this error.

Does anyone know how to eliminate this error?

Thank you!

John