Edit: This turned into a longer post than intended as a bunch of random (and not so random) ideas came to me. Do any of these sound useful? It might be better than fighting with Telkom about an issue which isn't theirs.
Ok, so here's a wild idea ... is it possible that your two routers are forcing each other to look for 'clean air'? I'd like to know whether this problem repeats with only a single router switched on .
My rough understanding of it is that a router will always hunt for a channel with the least use on it, giving you less distortion or some such. Now just maybe having two routers of the same kind in close proximity makes them go crazy, as they try to escape each other in exactly the same fashion.
Or... maybe there's something in your vicinity that throws out a massive pulse that overwhelms all local WIFI networks. Portable nuclear generator? Even better!
If the above doesn't help, you can easily try another WIFI router by sharing your phone's network connection through a portable WIFI hotspot (assuming you have a modern smartphone - these days even BlackBerries can cast portable hotspots). That won't be drawing the Internet connection from your ADSL obviously, but it might help you isolate whether there is something *external* in your neighbourhood which is knocking out all WIFI.
Finally I have one last guess for you: electricity fluctuations. This is a real thing, and it seriously affected my wife's router at work. When her boss turned on a particularly high-draining electrical device, it would cause a temporary brown-out to the whole office and cause the router to lose the connection. That was a wired connection, but my guess is it'd affect WIFI too: electricity dips, and router then has to re-start.
If it's a device you or your wife are turning on, just stop doing that. If it's something a neighbour is doing, you might need a UPS to stabilise your routers' electricity supply.
You can isolate whether or not your specific routers are at fault by just taking them to a friend with ADSL and asking him to use them for a while. If the problem doesn't replicate outside of your environment, chances are it's not the routers' fault.
