I'd guess the problems are unrelated... your dropping WiFi is the problem, and RDC is just sulking when it can't connect.
You could eliminate that by running a VNC server on the Windows machine and a VNC client on the Mac and see if the same problem happens
I use RDC a lot to connect to both machines here and in remote data centres and don't have a problem... I've got timeouts on remote machines set to 10 mins, so if my WiFi (or GPRS) connection drops I've still got time to get back in and resume !