Customer calls, saying they are having difficulties accessing their email (and other strange dropouts) while using their bigpond 3G usb adapter.

Once I get there, I find its all behaving itself normally… no problems (except for VISTA running on 512MB RAM!).

I try various things to try to force the problem to appear, but the email, web browsing, and updates are faultless.

Customer says when the dropouts happen, they usually need to restart the laptop… but strangely, the laptop works well at other locations. They even have an external antenna for the 3G adapter, so that the signal strength cant be an issue.

I also note that when I connect to the 3G network, it takes about 5-10 seconds to connect… no unusually long delays.

Out of curiosity, I look at vistas available networks, and besides the 3G network, it can also see a weak, unsecured 802.11G wireless network… and this is where all the symptoms start to make sense.

I know that XP (and I extrapolate that VISTA has the same weird behaviour) will sometimes prefer to connect to a very weak wireless network rather than other networks (sometimes even ignoring wired ethernet!).

I’m told a neighbor has a wireless router (I reckon its the unsecured network I saw on the laptop).

What I think has been happening, is that the laptop will connect using 3G, and then decide to automatically switch connection to the 802.11G network next door… So now emails refuse to work, as the neighbor is with a different ISP, and web browsing can be badly affected.

What could also happen, is that the laptop connects to 802.11G before it gets manually connected to 3G, so some leftover 802.11G settings cause problems with the 3G internet.

The solution is very easy: push the wireless enable/disable button on the laptop, and the 802.11G network/antenna is disabled.