Thank you for your time and willingness to help me.
My OA version is 188.8.131.52 ( paid ). My router is a SonicWall TZ180 Wireless. The wired desktops and wireless laptop all run Win XP Pro SP3. They all run the same OA version and the same security software. I have contacted SonicWall, but together we identified the issue as the OA Firewall since without the firewall active the desktops and laptop can communicate across the subnet boundary.
Your thoughts are most welcome, and again, thank you for taking time to share your knowledge and experience. Please let me know if you would like additional configuration information.