Hello:
Are you running version 8.0A of Receivables? If so, check the Service Pack version (go to Help | About and look for the date in brackets after the version number).
If you are using a Service Pack older than 051026 (Oct 26/2005) then the problem described by Andrew is the culprit. The transactions were removed from "Current" but not transferred to "History" during Year End.
If you have a more recent Service Pack but haven't been running Month Ends, have you looked in the list of "Current" transactions for the Dec. to Apr. transactions? It is possible to select a date during Year End that leaves the transactions as "Current".