10G agent and Listener hangs on Windows 2003 64bit?

We have recently migrated our Oracle 10gR2 (10.2.0.3) database from Windows 2000 32 bit to Windows 2003 64 bit as we were getting constant memory problems. The virtual bytes would continually increase till the database would hang.

Anyway, now the 10G agent and the Oracle Listener keep hanging on the Windows 2003 64 bit server. We have to resort to a reboot to clear the problem. Does anyone know of any problems relating to this? Thanks. Rgds. Sheryl