Subreport shows in preview but not when running

Hello!

I have some reports, all of which contain one or more subreports. All work fine in the preview window but some do not display the subreport information when I run them through my application whereas others do. I haven't set them up any differently so am baffled as to why they are behaving so differently!

When I click on the area where the subreport should be, it displays it in a different window, but I want it to be displayed as part of the main report.

Does anyone have any ideas?

Thanks!