Hey there cumbrianblues, and welcome to the eForum!
I've never seen this happen on Windows 7 with the latest versions of VMC
There was a similar problem on Vista, but that was resolved with an update. I don't have a solution for you right now, but it does sound like how your machine is prioritising connections - as if it's still trying to connect via VMC even with WLAN present.
Can you try the modem on another computer? Does the same occur?
I will ask around the team for some advice and get back to you when we know more! In the meantime, any extra detail you can provide will really help!
Daz
eForum Team