Report Error: Index was out of range

I found an unusual error message at a school – again running report in back-office was okay, but got an error in spider as below:

“Index was out of range. Must be non-negative and less than the size of the collection. Parameter name”

I found the report had two data-sources listed i.e.

• C:\PCSSQL\PCSchool\Reports\SQL\PCSchool.mdf.dsn
• D:\PCSSQL\PCSchool\Reports\SQL\PCSchool.mdf.dsn

I fixed the issue by updating the data-source(s) to be one consistent location, and then validating the report.