Recently, I faced a strange problem.
One of my crystal reports had a sub report.
The sub report was displaying data partially though the entire data was made available to it.
This is a push method where Dataset gets formed and assigned as datasource to the crystal reports using SetDataSource method.
After hours of digging, I finally found out that, if you have sub reports, always set the datasource of the subreport and then set the datasource to the main report.
Hope it helps.