Devices drop off network when switching from wired to wireless connection

[unclegym]

I have a networked AV receiver and a Windows7 laptop -- both with wired (CAT5e) connections to my Actiontec Rev-F router.  From the receiver, I can connect to my laptop (it shows up on the receiver GUI as a 'media server') and stream music files from my PC through the receiver.  Works like a charm until I switch the PC to a wireless connection.  As soon as I do this, the laptop 'disappears' from the receiver's menu and i can't reconnect until I plug in the CAT5.

I've reset the router and the receiver but the same thing keep happeneing.  It's like I have 2 separate networks that aren't seeing one another.