Why a PC with multiple adapters on the same network can cause trouble

I had my Windows XP laptop connected to my home “workgroup” network with wlan and ethernet network adapter at the the same time. Normally one would guess, just as this Microsoft KB article suggests, that this might not be benificial, but at least it does not do much harm either.

Well, guess again. The “double connection” caused my XP PC to not show up on the windows network any more and any connections between the windows XP and the windows 7 pc would fail.