No problem Wheeler, always a pleasure :-)
There are 2 parts to the network connection, data download - that's you getting the network tracks from the AirNav server, and data upload - that's you sharing your live data with the server.
You stop data download by unticking the "Network Flights" box below the Network aircraft list and you stop upload by deselecting "Share Flight Data" in File | Preferences.
My RB tends to take a few seconds on startup to connect to the server to get network traffic - it looks like its frozen, but it's just "thinking" and then the network tracks appear. If the server is down, after this short pause, I just get "0" in the network aircraft list and live tracks show fine.
The autopopulate doesn't seen to cause a problem if the server is down, all that happens is that nothing gets populated.
If I'm running RB without an Internet connection, I tend to deselect "Share Flight Data" as sometimes RB attempting to upload live data causes the program to slow down a bit. Leaving the "Network Flights" box ticked doesn't seem to be a problem with no Internet.
I presume that you are running V1.5 - I've probably asked this already :-)