Report export drops sub report - any ideas?

Hi All

When I export a report to Rich Text Format or the Snapshot Format a
sub report is being dropped which holds most of my data. This also
happens when printing with CutePDF Writer. The sub report just does
not appear at all - I just get blank space!

My report is laid like this:
* sub report in header with company details - this comes out fine
* controls and some data in the form detail pane - - this comes out
fine
* sub report in the form detail pane which lists rows of data - the
items most important for the report - this sub report is dropped
altogether!!
* sub report in footer with more company details - this comes out
fine

Has anyone had any similar problems?

Thanks in advance for any hints,
Chrisso