In many cases if
SPDataSource has been changed to
CrossList mode, paging settings previously applied to a single list view no longer worked correctly; the paging control shows an infinite number of entries. One workaround is to set paging to show all items by selecting the Display All Items option from the ribbon’s Paging command drop-down selection. However, this might not be a practical solution where you have a large number of items and want to limit the items to something like 10 per view (or dataset).
See http://social.msdn.microsoft.com/Forums/en-US/sharepointcustomization/thread/1e0a0263-3fcf-47ba-91cb-480d686bec25/ for further insight into working with paging and security trimming in