If you try to insert a subreport and you get the following error:
"com.crystaldecisions.sdk.occa.report.lib.ReportSDKException: Unexpected database connector error---- Error code:-2147467259 Error code name:failed"
It means that you need to rename your "Subreport Name".
To do this go to your main report and right click on the subreport, select "Format Subreport...", select the Subreport tab at the top, update the "Subreport Name:" to match your java PojoDataset tablename.
I sure wish that would have been somewhere that I could have read.