Are you using static IP address for your Macintosh connected via Wireless LAN as well?
Also, I understand that you are not allowed in - but we wanted to look at the connection drop problem first. So if I understood you right, the connection should survive for more than 15 mins.
Now, with regards to the login problem, please do kindly try the following:
Go to your Windows 7 implementation running in Parallels Desktop V5.
Make sure the network connection is bridged, not shared.
Open the command console (Start / type cmd in the Search programs box / hit Enter).
write PING plus the Beomaster's IP-address (e.g. ping 192.168.3.15) and hit Enter.
The program will now ping the Beomaster and supply back a delay time of anything between 10 and 200 ms.
Tell me if that worked for you.