A business customer has found that his PC suddenly, no longer connects to the internet. Also as a separate issue, a colleagues laptop is also unable to connect via the office wireless router.

The PC is straightforward: the network settings had been changed from automatically obtaining ip address & dns, to having a fixed (wrong) ip address & dns. I cannot explain why it happened (xp shouldn’t do this sort of thing, and there are no viruses & malware present)

The second issue is a bit stranger, as I had setup the centrino wireless on the laptop just a few days earlier. However, there is something different: a pcmcia card with a cute little antenna. I’m told its a 3G wireless internet card, as they need to use the laptop while out at an airport hanger.

So after some testing I eventually try unplugging the 3G card & restarting the laptop: then the 802.11G wireless starts working correctly.

Without spending hours testing different scenarios, I assume that the 3G card interferes with the 802.11g radio signals.