Our current implementation of jasperreports implements datasources as a Collection of IMObjects stored as an iterator.  Iterators by nature are not resetable unless you have access to the original dataset in which case you can simple overwrite the variable to reset it.  

It may be better to switch the implementation to cover JRRewindableDataSource, which requires to the moveFirst() method to be implemented.

This would mean that all subreports that use a Dataexpression to generate the datasource as opposed to a sql datasource will be presented with a datasource that can navigate a page break - currently they do not.

I have reported this issue here before but I was using a custom report.  However a user of 1.6 is reporting it now using the default reports.

http://www.openvpms.org/forum/monthly-statement-printing-error

http://www.openvpms.org/forum/error-when-doing-statements.-what-does-mean

http://www.openvpms.org/forum/custom-statement-wont-print-certain-custom...

here is the new implementation

http://jasperreports.sourceforge.net/api/net/sf/jasperreports/engine/JRR...

The quick fudge for this is changing the iterator to a ArrayList before passing it to the collection and storing it there as an ArrayList.  Effectively in movefirst you can just replace the iterator with the original array. 

It would probably be better to rewrite the module getting rid of the iterator all together and working of an ArrayList using its methods to move throw the datacollection.