So far as I know it only affects Netgear routers, not the Thomson boxes supplied by O2 and Be. It also only occurs when they are left idle for a fair while, not while downloads are taking place so shouldn't worry you.
It takes a few seconds to fix by going into the GUI of the Netgear when it occurs. I have had to do it less than a dozen times since it was first reported and it doesn't bother me in the least.
Note that the people posting about it are in general continuing to use their Netgears rather than the O2 boxes, and not a single one has suggested they might leave because of it.