As I’ve written about before, I use a combination of Vodafone 3G and the AT&T Network Client on Windows to access my corporate VPN. Recently, I’ve been seeing this error a lot when ‘dialling’ the 3G network (I connect it via the Windows dialler, rather than the Vodafone client):
This morning, I figured out what it was that was causing the problem. AT&T was open when I was dialling, and had the modem selected in the ‘Cellular’ tab (which I don’t normally use):
I hypothesise that it’s got a lock on the modem when this is selected (even if the ‘Cellular’ tab is not selected). Quitting the AT&T client appears to allow the connection to be created. You can then restart it and connect to the VPN in the normal way (using ‘existing internet connection’).
Hope this helps someone.